Chapter 3. Assessment of Fetal Well-Being
Fetal surveillance is utilized to assess well-being. There are several modalities available to accomplish this task. During the antepartum period assessments may include the non-stress test (NST), contraction stress test (CST), amniotic fluid volume (AFV) assessment, biophysical profile (BPP), Modified BPP (includes an NST and AFV), Doppler velocimetry, and fetal movement counts. During the intrapartum period assessment is generally accomplished through the use of fetal monitoring by auscultation or application of the electronic fetal monitor. Our understanding of the limitations of fetal surveillance, as well as the benefits, has changed dramatically over the years and will continue to change as new technology and practices are supported. The body of evidence to support the use of technology into our practice continues to increase. The goal of these evidence based findings is to support improved patient outcomes.
PHYSIOLOGY AND PATHOPHYSIOLOGY OF FETAL OXYGENATION
Maternal Circulatory and Cardiovascular Adaptation
One of the most dramatic adaptations to pregnancy is the increase in maternal blood volume by 20% to 100% over prepregnant volume. Plasma increases plateau around 32 to 34 weeks of gestation. The number of red blood cells increases in response to the plasma volume. Both volume and blood cell increases are in response to cell proliferation and growth of the uterus, placenta, and fetus.
Under physiologically nonstressful conditions, the vascular system in the maternal pelvic region remains widely dilated. In the presence of stressors, it is capable of marked constriction and reduction of uteroplacental blood supply. The most common and easily preventable stressor is mechanical obstruction of the maternal inferior vena cava and aorta by the gravid uterus when in a supine position. Activation of the maternal autonomic nervous system (ANS), in response to other hemodynamic changes, may also trigger marked constriction of the pelvic vasculature, which is physiologically expendable to general maternal circulatory needs.
The usual state of the uterine vasculature is one of low resistance to blood flow. This occurs in part because of new vascularization of the uterus and in response to the systemic influence of estrogens, which increases overall vasodilation. It is now estimated that uterine blood flow increases from 50 ml/min in early pregnancy to 700 ml/min by term.
Because of vasodilation and increased volume, cardiac output (Stroke Volume × Heart Rate) is greater during pregnancy. The heart rate is generally 10 to 15 bpm faster than prepregnant rates, and stroke volume is increased by approximately 15% because of increased blood volume. The increase in cardiac output helps circulate more blood to the uterus during pregnancy.
UTEROPLACENTAL-FETAL EXCHANGE∗
The placenta performs several major organ functions for the fetus. It acts as the following:
• Lung for respiratory functions of exchanging oxygen (O
2) and carbon dioxide (CO
2)
• Gastrointestinal tract for nutritive functions and exchange of waste products and electrolytes
• Skin for thermoregulation
• Kidney for renal functions of acid-base balance and electrolyte homeostasis
• Endocrine organ for production of hormones that promote placental perpetuation
• Barrier to maternal blood and bacteria
After implantation, the placenta begins to form the chorionic tissues. By 14 weeks, the placenta is a discrete organ with independent functions and purpose. It is at this point that segments of the placenta, called
cotyledons, form and connect by vascular channels to the umbilical cord. The surface of the placenta then thins to a membranous, single layer of cells. Maternal blood and fetal blood, although not mixing, are exposed to one another across this membrane. By this exposure, fetal respiration, acid-base and electrolyte homeostasis, nutrition, and excretion take place. The space in which these functions take place is the intervillous space, which contains maternal blood. Therefore, the fetus totally depends on its mother for most homeostatic mechanisms.
Transfer and exchange of molecules occur in the intervillous space. Molecules enter through the epithelial cells on the surface of the villi and move through the villous stroma and into the fetal capillary vessels within the villi. Molecules pass back and forth between maternal and fetal tissues. Transport increases during gestation, caused by changes in the structure of the placenta, increased fetal and maternal blood flow, and fetal demands. Transfer may be modified by maternal nutritional status, exercise, and the effects of disease (i.e., diabetes, hypertension). Exchange processes are accomplished by means of simple or selective diffusion.
Simple (passive) diffusion is a relatively uncomplicated process responsible for the rapid exchange of small molecules, such as O
2, CO
2, water, electrolytes, creatinine, and uric acid, across the placental membrane. Simple diffusion also allows potentially harmful drugs—antibiotics, narcotics, barbiturates, and anesthetic agents, to name a few—to cross quickly to the fetus. Simple diffusion depends totally on the adequacy of uterine blood flow and the concentration gradient of the molecules.
Facilitated diffusion is a complex process and therefore occurs more slowly than simple diffusion. It can occur against a concentration gradient by an energy-dependent process. Glucose, for instance, is transported in this manner from stores in the placenta.
Selective transfer can also be actively facilitated by specific enzyme systems. For example, through
active transport amino acids and buffering substances are transferred using specific enzyme groups to facilitate the process. Selective transfer, by energy- or enzyme-dependent processes, depends on the sufficiency of the placental surface area and placental thickness rather than on uterine blood flow.
Because simple diffusion is faster (taking only minutes), O
2, CO
2, and water can be transported and exchanged rapidly to correct fetal hypoxia if uterine and umbilical blood flow and maternal O
2 are sufficient. On the other hand, the more complex processes of selective transfer, which take hours, cannot correct an acid-base imbalance from hypoxia.
Fetal Capabilities for Maintaining Health
The fetus has certain remarkable capabilities that enable it to withstand stressors. Fetal stressors may be caused by physiologic maternal adaptation failures, disease, or mechanical or physiologic obstruction of maternal blood flow through the uterus and into the intravillous space. The fetus is equipped with a high concentration of hemoglobin in plasma (60% hematocrit). Each hemoglobin molecule, because of its unique shape, can be supersaturated with O
2. This is fortunate and necessary because by the time maternal O
2 is transferred to the fetus, the O
2 partial pressure (P
o2) is at best 35 to 40 mm Hg. Compared with an adult P
o2 of 90 to 96 mm Hg, the fetal P
o2 would be inadequate were it not for different fetal hemoglobin. The low fetal P
o2 causes the diffusion gradient to facilitate O
2 delivery from mother to fetus (Meschia, 2009).
The fetal heart must be significantly hypoxic before myocardial depression occurs. It is only after fetal myocardial depression that significant fetal central nervous system (CNS) hypoxia occurs. Protection from myocardial hypoxia exists, in part, because of the well-supplied and unimpeded blood supply from the coronary vessels. Impulses travel through the heart, originating at the sinoatrial node and traveling across the atrioventricular junction, down the bundle branches, and out the Purkinje fibers in the ventricles. When myocardial depression occurs from hypoxia, cardiac arrhythmias may occur. The fetus can effectively compensate only by increasing FHR; it cannot increase output by changing cardiac output.
Function of Amniotic Fluid Related to Evaluation of Fetal Heart Rate
Early in gestation amniotic fluid is produced primarily by maternal blood. By week 11 of gestation the fetus contributes to the volume through urinary excretion. Amniotic fluid has a number of functions. It is a buoyant medium, allowing the umbilical cord to float and preventing it from becoming entrapped between the wall of the uterus and the fetal body, especially during contractions. This function is imperfect but, for the most part, effective.
PHYSIOLOGIC BASIS OF FETAL HEART RATE CONTROL
Central Nervous System Control
Regulation of the FHR originates in the fetal CNS. By week 10 of gestation, both the CNS and the cardiac system are developed enough to begin and maintain the FHR.
Sympathetic
Initially, the sympathetic portion of the rudimentary ANS is functionally active. The sympathetic branch is responsible for establishing and sustaining FHR. The normal rate throughout fetal life ranges from 110 to 160 bpm for most, tending toward the upper range of 150 to 160 in early fetal life and the middle to lower range of 110 to 140 by term. The sympathetic branch of the ANS supports acceleration of the FHR in response to various stimuli, as needed for fetal circulation, and supporting compensatory responses to physical insults.
Parasympathetic
Early in fetal life, the parasympathetic branch of the ANS begins to influence the FHR. The parasympathetic branch serves as an opposing force against the steady beat sustained by the dominant sympathetic branch. This opposition exerts a differing strength of opposing force on each beat. The effects of this opposing force are observed on the FHR as it gradually slows the intrinsic rate from early gestation through term gestation.
The opposition between the sympathetic and parasympathetic nervous systems results in visual fluctuations in the FHR over time referred to as variability. Beat-to-beat differences in the FHR have been referred to as
short-term variability and cyclic fluctuations that occur over a minute have been referred to as
long-term variability. There is no current evidence that the distinction between short- and long-term variability has any clinical significance. Because they are visually determined as a unit the National Institute of Child Health and Human Development (NICHD) do not recommend differentiating between the two (Cunningham, 2010).
FETAL HEART RATE MONITORING
Electronic Monitoring
Electronic fetal heart monitoring (EFM) provides a current and continuous observation of indirect, subjective information about fetal oxygenation at the time the monitoring is being done. Continuous or intermittent FHR tracings provide a convenient and reasonably predictable way of assessing fetal well-being. Of approximately 4 million live births in 2002, 85% were assessed with EFM in the United States (ACOG, 2009). It does not explain oxygenation in the past or predict the future oxygenation during fetal life in the same way we once expected. When EFM was introduced in the 1960s it was believed the continuous recording would prevent fetal deaths and decrease cerebral palsy. Thus the use of the fetal monitor was accepted despite the lack of evidence to support this practice.
U.S. health statistics from 2005 indicated that overall infant mortality (deaths per 1000 live births) was at 6.86 in 1000 births (MacDorman and Mathews, 2008). The United States was ranked 29th among industrialized nations based on available data in 2004 (MacDorman and Mathews, 2008).
In the United States, continuous EFM is routine in most hospital perinatal/maternity centers. Given the available data, ACOG (2009) stated that intermittent auscultation or EFM are acceptable options for a patient without complications. A Cochrane meta-analysis (Alfirevic, Devane, and Gyte, 2006) on EFM included a review of 12 trials that identified no difference in the perinatal death rates or incidence of cerebral palsy. Other data from the review of these 12 studies showed that neonatal seizures were decreased by half, but there was an increase in the number of cesarean births and operative deliveries.
Perinatal mortality has improved over the years, and EFM is one reason for the improvement. However, morbidity statistics have not improved, raising three main concerns regarding routine use of EFM (Thacker et al., 2001 and American College of Obstetricians and Gynecologists (ACOG), 2009):
• Effects of EFM on the incidence of cerebral palsy (CP)
• Effects of routine continuous EFM on cesarean birth rates
• Legal implications of FHR assessment (Mahlmeister, 2000)
Cerebral Palsy
The Centers for Disease Control and Prevention (CDC, 2006) estimates the rate of CP to be 3.6 per 1000 children. This rate has not decreased with the advent of the use of EFM. In fact, because more premature infants are surviving and because they have an associated increased risk for congenitally acquired neurologic damage, CP rates are unlikely to improve (Phelan and Kim, 2000 and Freeman et al., 2003). There is also some suggestion in the literature that CP actually may start with the development of an abnormal fetal brain (Phelan and Kim, 2000). A large percentage of asphyxial damage occurs before labor and thus would not benefit from electronic FHR monitoring-prompted interventions offered during labor (Freeman, 2002 and Freeman et al., 2003).
Cesarean Section
The most discussed risk of EFM is the rise of cesarean birth rates. In the United States, the current cesarean birth rate is 31.8% (Hamilton, Martin, and Ventura, 2009). One study examined the cesarean birth rate in more than 7000 births at a large Southwestern tertiary perinatal center in a more divided manner (Radin, Harmon, and Hanson, 1993). In this study, term primiparas, regardless of demographic data, physician practice, complications, induction, regional anesthesia, or stage of labor when admitted, had an 18% cesarean birth rate. Excluded from the study were those with multiple gestations, those with intrauterine fetal death, and those who were less than 35 weeks pregnant.
Three discrete groups of nurses were identified. The low cesarean birth rate group had a cesarean birth rate lower than 5%. The middle cesarean birth group had an overall 18% cesarean birth rate. The highest cesarean birth rate group had a rate as high as 35% to 49%. No significant differences existed in neonatal Apgar scores. This study suggested that some nurses may manage technologic data from EFM to provide expert nursing care and manage patients with epidurals differently, whereas other nurses may use the data solely to report fetal assessment data to the physician to alter medical management. This study warrants further investigation of specific differences in the patient population, and nursing care practices, including designation of patient care assignments.
Legal Implications
In the care of the antepartum and intrapartum patient, accurate interpretation of FHR patterns is essential. One challenge that has been identified is the lack of consistent terminology and definitions in describing fetal heart patterns. Simpson (2004) identified this as a critical issue and recommended the need to select one set of definitions for fetal heart rate patterns and the need to communicate consistently to avoid confusion between health care providers.
In April 2008, the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), the American College of Obstetricians and Gynecologists (ACOG), and the Society for Maternal-Fetal Medicine partnered to sponsor a workshop with three goals:
• To review and update FHR definitions
• To assess existing classification systems for interpreting specific FHR patterns
• To make recommendations for research priorities for EFM (Macones et al., 2008a and Macones et al., 2008b)
The incorporation of these terms into practice has also been endorsed by the Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN, 2009).
Failures in communication have been identified as a contributor to birth injury litigation (Knox, Simpson, and Garite, 1999). McKeon, Cunningham, and Detty Oswaks (2008) suggest the need for effective communication as a strategy to improve patient safety. Working in complex work environments, health care providers can support prevention of adverse fetal outcomes through the use of a standardized “language.” Incorporating standardized FHR definitions into practice will prevent failure to report fetal monitor strip information or pursue chain of command, failures related to intervention, those related to interpreting the fetal monitor tracing, and failures related to contacting the health care provider.
Intermittent Auscultation
Feinstein, Sprague, and Trepanier (2008) suggest that institutions develop protocols and policies to support the use of intermittent auscultation (IA). They identify the importance of listening to the FHR immediately after a contraction for at least 30 to 60 seconds. During that 30- to 60-second period of time the need to identify a baseline and the fetal response following the contraction must be assessed. Differentiating the maternal pulse from the FHR must also be accomplished. The nurse must place a finger on the woman’s radial pulse as part of the assessment.
ACOG (2009) identified that although intermittent auscultation may not be appropriate for all pregnancies, it may be acceptable in the patient with no complications. When a woman requests IA during labor the care providers must collaborate. Areas to consider are the woman’s perspectives, preferences, risk factors, staffing, practitioner’s experiences, and institutional guidelines (Feinstein, Sprague, and Trepanier, 2008). Research in support of this technique will make IA a more desired option for certain identified populations.
With research findings supporting the use of both EFM and IA, it is apparent that perinatal nurses must understand how to use FHR monitoring. To do this, perinatal nurses must be fully acquainted with the following (Haggerty and Nuttall, 2000 and Schmidt, 2000):
• Physiology and pathophysiology of fetal oxygenation
• Physiologic basis of FHR control
• Instrumentation and the application of external and internal fetal monitoring methods
• Baseline FHR, variability patterns, periodic rate changes, arrhythmias, and artifacts, which describe effects of maternal contractions on FHR control
• Nursing management related to EFM
• Skills and techniques for antepartum evaluation of fetal well-being through auscultation, EFM testing, and fetal movement counts
• Advanced methods of fetal evaluation, such as biophysical profile and Doppler flow studies
Instrumentation and Application of Fetal Monitoring Methods
Although still indirect and somewhat subjective, EFM gives data slightly more objective than intermittent auscultation and infers information about current and ongoing fetal oxygenation. It does this by calculating and recording an average FHR per minute, indicating the baseline rate and variability, and by providing a continuous graphic printout of rate patterns and periodic changes.
To fully appreciate EFM patterns, it is helpful to have a continuous record for interpretation. Correct application of monitor methods and an understanding of the way to properly operate the monitor help the user obtain accurate information. Fetal monitors are made by a variety of manufacturers and may have capabilities for external (indirect) monitoring only or for both external and internal (direct) monitoring of FHR and maternal contractions (Fig. 3-1). Other features, such as fetal electrocardiogram (ECG) monitoring, twin monitoring, amnioinfusion, ambulatory monitoring, electronic transmission of strips from one location to another, central displays, and computer record storage are available from most manufacturers.
 |
| Figure 3-1 A, Avalon FM30 transducer.
B, Corometrics Model 129 maternal/fetal monitor provides measurement of FHR, fetal oxygen saturation, UA, and maternal parameters, including Sp
o2, ECG, FHR, and noninvasive BP. The audible and visual “spectra alert“ option may be added to this monitor. (
A, Courtesy Philips Medical Systems, Andover, MA.
B, Courtesy GE Medical Systems Information Technologies, Milwaukee, WI.) |
External (Indirect) Monitoring
The external monitor parts are the ultrasound transducer (Fig. 3-2,
A) for assessing FHR and the tocotransducer (Fig. 3-2,
B) for assessing contractions. To place the transducers properly, it is important to ascertain by abdominal palpation how the baby is positioned.
 |
| Figure 3-2 External monitoring includes the ultrasound transducer and the tocotransducer.
A, Ultrasound transducer is placed over the fetal chest wall facing the fetal heart.
B, Tocotransducer is placed over the best palpated area of the uterus, usually near the umbilicus near term. |
External contraction monitoring
Near term, the tocotransducer should be placed over the fundus of the uterus, two to three fingerwidths below the top and slightly off center from the umbilicus on the side where the fetal back is palpated. A good rule of thumb for placement of the tocotransducer for preterm contractions is to palpate the uterus for firmness and place the tocotransducer where this is best felt. The placement may be in any quadrant, including those lower than the umbilicus. There is a pressure-sensitive area on the underside of the tocotransducer that must respond to changes in the abdominal wall when the uterus contracts against it. The tocotransducer is secured in place with a belt that is tightened only enough to keep it from slipping or it is secured with a stretchy band. The monitor has an indicated dial or button to artificially set the reference for uterine resting tone, usually between 10 and 20 mm Hg on the graph paper. Box 3-1 presents the advantages and limitations of external contraction monitoring.
Box 3-1
Advantages and Limitations of External Contraction Monitoring
Advantages
• Noninvasive
• Convenient
• Provides continuous record of frequency and duration of contractions
Limitations
• Cannot accurately measure strength (intensity)
• Restricts patient movement or must be adjusted frequently with position change
Modified from Tucker S, Miller L, Miller D: Mosby’s pocket guide to fetal monitoring: a multidisciplinary approach, ed 6, St Louis, 2009, Mosby.
External fetal heart rate monitoring
The ultrasound transducer has sending and receiving crystals encased in a disk. If possible, it should be placed over the fetal back for detection of the best signal. The signal is detected from the motion of the heart valves closing between the atria and ventricles.
The ultrasound transducer selects the complex of two sound waves from the motion of the two atrioventricular valve closures, or it selects the one sound wave that is timed within the logical sequence of events; then it calculates the rate per minute. Through a system of logic, it samples a set number of valve closures, compares the previous intervals, and decides which to count. The logic system tends to give the appearance of slightly greater rate differences than are truly present. This causes the appearance of “roughness“ or a “jiggle“ to the line (Freeman, Garite, and Nageotte, 2003). Because there are still different generations and models of equipment in use, it is important to recognize the parameters and to know from which era the monitor in use comes. If the rate differences are not logical compared with the previous calculated rates, blanks will appear in the tracing. Blanks also occur when the signal is lost from fetal movement or shift in maternal position. Box 3-2 presents the advantages and limitations of external FHR monitoring.
Box 3-2
Advantages and Limitations of External Fetal Heart Rate Monitoring
Advantages
• Noninvasive
• Does not require dilation or membrane rupture
• Convenient
• Continuous recording of fetal heart rate (FHR)
• Can assess changes in baseline, variability, accelerations, decelerations
Limitations
• Tracing quality affected by maternal position, obesity, and fetal movement
Modified from Tucker S, Miller L, Miller D: Mosby’s pocket guide to fetal monitoring: a multidisciplinary approach, ed 6, St Louis, 2009, Mosby.
Internal (Direct) Monitoring
Internal monitoring uses different components: an intrauterine pressure catheter (IUPC) (Fig. 3-3,
A) and a fetal spiral electrode (FSE) (Fig. 3-3,
B). An IUPC monitors the frequency, duration, and intensity of the contraction and the resting tone of the uterus. The FSE monitors the fetal electrocardiogram.
 |
| Figure 3-3 A, Intrauterine pressure catheter.
B, Fetal spiral electrode for attachment to leg plate. (Courtesy Kendall-LTP, Chicopee, MA.) |
Intrauterine pressure catheter
The IUPC may be inserted by qualified registered nurses (RNs) if this is allowed according to regulations of each state’s nurse licensing board. In addition, individual institutional policies and procedures are adhered to.
The IUPC catheter is inserted before the spiral electrode, in an aseptic manner, into the uterine cavity. The catheter is a flexible, narrow-gauge tube with holes along a short distance and at the proximal end. It is partially enclosed in a firmer plastic catheter introducer. Once amniotic membranes are ruptured and the cervix is adequately dilated, the IUPC can be placed, allowing uterine pressure monitoring, amnioinfusion, and fluid sampling. The two types of IUPCs are a fluid-filled catheter (not used as commonly) or a solid catheter. The differences between these two include setting up the equipment and the procedure for zeroing the monitor. Zeroing the monitor must be accomplished according to the individual manufacturer’s instructions.
The examiner’s hand carefully lifts the presenting part and inserts the introducer with the catheter just through the dilated cervix. Then the catheter is carefully advanced to a specific marker visualized on the outside of the perineum. The introducer is drawn back toward the distal end, and the catheter remains behind. The catheter is then secured to the patient’s thigh.
As the uterus contracts and relaxes, the intercavitary pressure is reflected against the catheter. The distal end is connected to a reusable cable that connects the disposable IUPC to the fetal monitor. Pressure of contractions is measured in millimeters of mercury (mm Hg).
Fetal spiral electrode
The FSE may also be placed by qualified RNs. It is attached to the presenting part of the fetus, avoiding such potentially dangerous areas as the fontanels, facial features, or genitalia, if breech. The FSE has two color-coded wires attached to it. These are twisted together, and all are encased in an introducer. The examiner identifies the area of the presenting part and then inserts the introducer between the fingers and flush against the presenting part. The distal ends of the wires are rotated clockwise until gentle resistance is encountered; thus the FSE is attached to the fetal presenting part. The introducer is removed, the end of the FSE is connected to a leg plate on the patient’s thigh, and the leg plate cord is plugged into the fetal ECG receiver on the monitor.
The monitor, in this way, directly counts from the fetal R wave (the highest amplitude electrical impulse from the fetal heart). It does not need to respond to or disregard other fetal impulses, but may count maternal R-R intervals if the fetus is dead. What is plotted on the graph paper is each rate from every R-R interval calculated, as it is, for 1 minute. Box 3-3 presents advantages and limitations of internal monitoring.
Box 3-3
Advantages and Limitations of Internal Monitoring
Advantages
Contractions are measured accurately for:
• Strength
• Duration
• Frequency
• Resting tone
More comfortable than external monitoring
Limitations
• Requires ruptured membranes and dilation
• If prolonged, ruptured membranes may carry a small increase in infection
• Possible injury to uterine wall or fetus if improperly inserted
In the presence of a fetal demise the FSE may record the maternal heart rate
Modified from Tucker S, Miller L, & Miller D: Mosby’s pocket guide to fetal monitoring: a multidisciplinary approach, ed 6, St Louis, 2009, Mosby.
Other Features on Monitors
Electronic fetal monitors frequently have other features for monitoring the mother. It is possible to monitor the pulse, oxygenation and maternal blood pressure, and print these recordings out on the monitor strips. In addition, this patient information can be automatically placed in a computer-based documentation system through the use of computer interfaces. Antepartum and intrapartum monitors are equipped with these capabilities. Also, there are remote devices for charting from a handheld keyboard to such things as physician visits, vaginal examinations, position changes, oxytocin (Pitocin) changes, and intravenous (IV) fluids given, and this information prints onto the monitor strip.
Electronic fetal monitors frequently have other features for monitoring twin or multiple gestations. For twins, two separate ultrasound transducers allow a continuous recording of each fetus. Easy identification of each fetus is provided electronically by the color coding on the computer screen. If a paper fetal monitor recording is used, differentiation between each fetus in a twin gestation can be identified by a thicker line tracing for one fetus and a thinner line tracing for the second fetus.
Cordless ultrasound and tocotransducers are available to allow the laboring patient to have increased freedom to ambulate while the fetus is continuously monitored. External watertight transducers are also available and can be used with wireless telemetry to allow for continued fetal surveillance during hydrotherapy or when the patient is using the shower or tub to promote relaxation.
Central fetal monitor displays allow for viewing of several fetal monitor tracings at one location. Remote viewing of these multiple displays is available on a computer screen, which may be viewed from several locations, including the nurse‘s station, locker room, physician’s office, or the physician’s home. Some of these electronic systems include audible alerts to identify a fetal heart rate outside preset fetal heart rate ranges. Alerts are also available for loss of signal if the patient moves or the fetus moves and the ultrasound transducer is unable to provide a continuous recording of the fetal heart tones (FHT).
Fetal Monitoring Terms
The 2008 NICHD updated fetal monitoring definitions defined
periodic fetal heart patterns as those associated with uterine contractions, and
episodic fetal heart patterns as those not associated with uterine contractions. They suggest the term hyperstimulation be replaced with the term
tachysystole, meaning greater than 5 contractions in 10 minutes, averaged over a 30-minute window (Macones et al., 2008a and Macones et al., 2008b).
Additionally the NICHD (Macones et al., 2008a and Macones et al., 2008b) has developed a three-tiered system to categorize FHR tracings. This three-tiered system includes
Category I, which is described as
normal, suggesting normal fetal acid-base status at the time of assessment. These tracings require routine care with no specific intervention.
Category II is described as
indeterminate and not predictive of abnormal fetal acid-base status, but cannot be assigned as Category I or Category III (abnormal) FHR tracings. These Category II tracings require evaluation and continued surveillance and reevaluation.
Category III FHR tracings are described as
abnormal and are identified as predictive of abnormal fetal acid-base status at the time of evaluation. They require prompt intervention to resolve the abnormal FHR pattern such as maternal position change, application of oxygen, treatment of maternal hypotension, and discontinuation of labor stimulation as appropriate. Box 3-4 summarizes the NICHD fetal heart rate categories and the patterns included in each category.
Box 3-4
NICHD Fetal Heart Rate Categories and Patterns
Category I
Normal suggesting normal fetal acid-base status at the time of evaluation.
Includes all of the following:
• Baseline rate 110–160 bpm
• Moderate variability
• Absent—late or variable decelerations
• Present or absent—accelerations
• Present or absent—early decelerations
Category II
Indeterminate and not predictive of abnormal fetal acid-base status but they are not able to be assigned as Category I or Category III FHR tracings.
Examples include:
• Bradycardia not accompanied by absent variability
• Tachycardia
• Minimal or marked variability
• Absent variability not accompanied by recurrent decelerations
• Absent or induced accelerations after fetal stimulation
• Recurrent variable decelerations accompanied by minimal or moderate variability
• Prolonged deceleration
• Recurrent late decelerations with moderate variability
• Variable decelerations with slow return to baseline, overshoots, or shoulders
Category III
Abnormal and are identified as predictive of abnormal fetal acid-base status at the time of evaluation.
Include either of the following:
• Absent FHR variability and any of the following: recurrent late decelerations, recurrent variable decelerations, bradycardia
• Sinusoidal pattern
Modified from Macones GA, Hankins GD, Spong CY, Hauth J, Moore T: The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines, J Obstet Gynecol Neonatal Nurs,112(3):510-515, 2008.
Can Category I, Category II, and Category III Be Applied to Intermittent Auscultation?
In an effort to support the use of a common language in the interpretation of fetal monitoring, the NICHD has also recommended the use of the three-tiered system when communicating about IA. Intermittent auscultation can be categorized as Category I
(normal) or Category II
(indeterminate) as stated in Box 3-5. However because Category III
(abnormal) uses information about FHR variability it is not feasible to categorize IA in Category III (AWHONN, 2009).
Box 3-5
Intermittent Auscultation Fetal Heart Rate Categories and Patterns
Category I— Normal
Include ALL of the following:
• Regular rhythm with normal FHR baseline between 110 and 160 bpm
• Presence of FHR accelerations (increases) from the baseline
• Absence of FHR decelerations (decreases) from the baseline
Category II— Indeterminate
Include ANY of the following:
• Irregular rhythm
• Presence of FHR decelerations (decelerations) from the baseline
• Bradycardia
• Tachycardia
Category III— Abnormal
• Unable to specify Category III because FHR variability information is not available.
Modified from Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN): Fetal heart monitoring: principles and practices, ed 4, Washington, DC, 2009, AWHONN.
The patient plan of care using the three-tiered system to categorize IA is based on a multitude of factors. A thorough and complete patient history and the events during the current admission must be incorporated into the communication between the members of the health care team. The plan of care can then be developed that is individualized and appropriate for the patient.
Fetal Heart Rate
The fetal CNS, specifically the ANS, controls the FHR. Because the ANS of the fetal brain is developed first, it is the most rudimentary. It requires a significant degree of hypoxia before FHR control shows the effects. Observation of Category I (
normal) FHR patterns predicts adequate CNS oxygenation. However, Category II (
indeterminate) features are considerably more subjective and of less predictive value for fetal oxygenation. In other words, little is known about how long it takes for what degree of hypoxia to occur (Freeman, Garite, and Nageotte, 2003).
Each examination of a fetal monitor strip should follow the same systematic steps:
• Evaluate patient history and status.
• Evaluate contraction frequency, duration, and if IUPC is used, intensity and resting tone.
• Determine the average baseline rate rounded to the nearest increment of 5.
• Describe FHR variability (fluctuations in the baseline).
• Identify accelerations, if present.
• Describe or, when possible, name patterns of periodic or episodic decelerations in the FHR.
• Describe changes in trends of the FHR pattern over 10 minutes or more.
Baseline Fetal Heart Rate
Baseline fetal heart rate is identified as the approximate mean FHR rounded in increments of 5 beats per minute (bpm) lasting at least 10 consecutive minutes and excludes accelerations, decelerations, and periods of FHR variability greater than 25 bpm (marked variability). In any 10-minute window the baseline duration must be at least 2 minutes or the baseline is described as indeterminate for that period. Therefore it may be necessary to review the previous 10-minute window to determine the baseline rate. The baseline FHR is always documented as a single number (145) and not as a range (140 to 150 or 140s) (Fig. 3-4). The baseline FHR is normally 110 to 160 bpm. Rates above 160 for more than 10 minutes are termed tachycardia (Fig. 3-5), and those below 110 for more than 10 minutes are termed bradycardia (Fig. 3-6). Table 3-1 summarizes baseline fetal heart rates.
 |
| Figure 3-4 Normal baseline FHR. Baseline FHR found between contractions, in absence of periodic changes, and observed in 10-minute segments
(panels 37317 through 37319 in center) is 150. This rate is within the normal range.
FHR, Fetal heart rate. |
 |
| Figure 3-5 Tachycardia. Baseline fetal heart rate
between panels 16272 and 16274 is 185 bpm. Arrows are result of maternal use of remote marker to indicate fetal movement. |
 |
| Figure 3-6 Bradycardia. Baseline fetal heart rate is 95 bpm. Moderate variability is present. |
| Tachycardia (Fig. 3-5) | |
| Description | Rate higher than 160 bpm for at least 10 consecutive minutes |
| Etiology | Acute, short-term hypoxia |
| Drugs given to mother, such as beta sympathomimetics (terbutaline, ritodrine) | |
| Stress | |
| Arrhythmia | |
| Fetal infection | |
| Maternal fever (may be caused by epidural analgesia) | |
| Maternal hyperthyroid disease | |
| Mechanism | Sympathetic response |
| Significance | Serious when >180 bpm |
| Nursing interventions | Look for cause |
| Turn patient to side | |
| Hydrate to improve circulating volume | |
| O 2 at 8–10 L/min by tight face mask | |
| Reduce stressors: turn off oxytocin (Pitocin); treat maternal fever | |
| Bradycardia (Fig. 3-6) | |
| Description | Rate <110 bpm for at least 10 consecutive minutes |
| Etiology | Chronic long-term hypoxia |
| Drugs such as beta-blockers (propranolol [Inderal]) | |
| Arrhythmia | |
| Terminal event after severe stress | |
| Prolapsed cord | |
| Mechanism | Parasympathetic response |
| Significance | Serious when <80 bpm or lasting >10 minutes |
| Nursing interventions | Turn side to side or to knee-chest position |
| O 2 at 8–10 L/min by tight face mask | |
| Correct maternal hypotension | |
| Look for cause such as prolapsed cord | |
| Prepare for delivery by most expeditious means | |
Baseline Variability
Variability is the most important FHR characteristic. It is the most important indicator of normal fetal pH or acidosis and reflects a healthy nervous system, chemoreceptors, baroreceptors, and cardiac responsiveness (Sweha, Hacker, and Nuovo, 1999). According to the National Institute of Child Health and Human Development (Macones et al., 2008a and Macones et al., 2008b), variability is defined as fluctuations in the baseline FHR that are irregular in amplitude and frequency. Grades of fluctuation are based on amplitude range. Variability is classified as the peak-to-trough in bpm:
A review of abnormalities of baseline variability can be reviewed in Table 3-2.
| ANS, Autonomic nervous system; CNS, central nervous system; FHR, fetal heart rate; IV, intravenous. | |
| ∗See Figure 3-7.
| |
| Absent Variability (seeFig. 3-7, panel 1) | |
| Description | Undetectable fluctuations in FHR |
| Etiology | Severe degree of hypoxia |
| Mechanism | Loss of interplay between branches of ANS |
| Significance | Category III status and indicative of fetal acidemia (pH <7.1) |
| Nursing interventions | Look for cause and treat by repositioning laterally Start and/or increase IV Give O
2 at 8–10 L/min by face mask Notify physician and report findings and intervention |
| Minimal Variability (seeFig. 3-7, panel 2) | |
| Description | Baseline FHR fluctuations <5-beat amplitude |
| Uncomplicated causes | Sleep, narcotic, barbiturate, or other CNS depressant; usually does not persist >60 min or length of initial medication effect |
| Problematic causes | Early hypoxia, congenital anomalies, fetal cardiac arrhythmias, extreme prematurity |
| Mechanism | CNS depression during sleep or after medication |
| Significance | Usually benign |
| Nursing interventions | Continued observation Acoustic stimulations |
| Marked Variability (seeFig. 3-7, panel 4) | |
| Description | Persistent cyclic fluctuations, of amplitude >25 bpm |
| Etiology | Recovery from previous insult |
| Response to sudden stimuli | |
| Stimulant drugs such as cocaine or methamphetamines | |
| Sympathomimetic drugs such as terbutaline | |
| Sudden hypoxia often associated with variable decelerations with a slow return to baseline or overshoots (Table 3-5 and Fig. 3-10) | |
| Mechanism | Increased interplay between sympathetic and parasympathetic branches of ANS or loss of ANS control |
| Significance | If persistent identified as a Category II fetal monitor tracing |
| Nursing interventions | Look for cause and treat by repositioning laterally Start and/or increase IV |
| Give O 2 at 8–10 L/min by face mask | |
Fetal Arrhythmia and Artifact
Fetal arrhythmias occur as a result of abnormalities in the automatic origination of impulses throughout the myocardium, a disruption of the normal impulse conduction pathway, or both. Some are benign, whereas others are pathologic.
To determine benign from pathologic fetal arrhythmias, features of both must be kept in mind. Those that are benign tend to appear in labor and disappear shortly after delivery. These neonates tend to have no heart abnormalities, neither anatomic nor functional. Pathologic fetal arrhythmias tend to be associated with certain maternal conditions such as lupus, illicit drug use, infection, and hyperthyroidism or fetal cardiac abnormalities; they also tend to be present and detected prenatally and are present during labor and persist into the neonatal period (Snyder and Copel, 2005).
Fetal arrhythmias usually can be detected as vertical lines through the baseline. Although these lines are sometimes so close together that they almost appear as solid blocks, the baseline can be found through them. There are rarely other problematic features about the baseline (Fig. 3-8).
 |
| Figure 3-7 Fetal heart rate variability is depicted in each panel. All are traced from a spiral electrode. 1, Absent. 2, Minimal. 3, Moderate. 4, Marked. 5, Sinusoidal. Original scaling, 30 bpm per cm vertical axis, and paper speed 3 cm/min –1 horizontal axis. |
 |
| Figure 3-8 A, Artifact. Note disorganized scattering of impulses traced by fetal scalp electrode.
B, Arrhythmia. Note organized distribution of impulses traced by fetal spiral electrode. |
 |
| Figure 3-9 A, Uniform acceleration is noted beginning in
panel 03727 in response to contraction beneath.
B, Nonuniform accelerations can be seen between contractions. Baseline fetal heart rate of 150 bpm with accelerations to 170 bpm. |
 |
 |
 |
| Figure 3-10 A, Early decelerations. Baseline fetal heart rate (FHR) is 145. Gradual decelerations begin when the contraction begins and end when the contraction ends.
B, Category III (
abnormal) variable decelerations. Note baseline of 130 bpm with a slow return to baseline and absent variability. Absent variability places this fetal monitor recording in Category III requiring prompt interventions.
C, Late decelerations. Baseline FHR is 150 bpm. Decelerations are seen with each contraction. Nadir of the decelerations occurs after the peak of the contractions. The absence of variability places this fetal monitor recording in Category III.
D, Prolonged deceleration in
panels 43786 and 43787. This deceleration followed initiation of epidural anesthesia and frequently can be avoided with intravenous fluid preload. |
 |
| Figure 3-11 Sinusoidal heart rate. A smooth, wavelike undulating FHR pattern with a cycle frequency of 3 to 5 oscillations/minute. |
 |
| Figure 3-12 Reactive nonstress test. Baseline fetal heart rate of 150 with accelerations of greater than 15 beats lasting for more than 15 seconds. |
 |
| Figure 3-13 Nonreactive nonstress test. No accelerations are seen that can be described as meeting criterion of 15 beats more than baseline for 15 seconds. |
 |
| Figure 3-14 Negative and reactive contraction stress test obtained with breast stimulation. No late decelerations are noted in any panel. Moderate variability is present, and fetal heart rate accelerates periodically. Three contractions are present in 10 minutes (
panels 01761 through 01763). |
 |
 |
| Figure 3-15 For legend see facing page.
A, Equivocal contraction stress test because of one late deceleration in
Panel 61145. Breast simulation was started to further challenge placental function and determine whether late decelerations would persist. Because remainder of test was negative for late decelerations and reactive, test was repeated the following day.
B, Equivocal contraction stress test because of uterine activity indicting tachysystole.
C, Equivocal contraction stress test, because tracing immediately following each contraction is unsatisfactory for accurate interpretation of fetal heart rate response. |
 |
| Figure 3-16 A, Positive contraction stress test with moderate variability. Tracing was continued, and reactivity was noted while decisions were made for delivery in postterm pregnancy.
B, Positive contraction stress test with absent variability. Baby was delivered by emergent cesarean birth with Apgar scores below 6. Mother was stable with preeclampsia. |
Artifact is a disruption of the normal logic system in the machine, which typically calculates the FHR by counting intervals of R wave to R wave. When it is unable to function in this way, the tracing appears as a garbled mess of vertical lines, through which one cannot identify a baseline rate or patterns. Table 3-3 describes and summarizes artifact versus arrhythmia, and Table 3-4 describes and summarizes dysrhythmias and their significance.
If a fetal arrhythmia is suspected, M-mode or spectral Doppler fetal echocardiography is most commonly used to diagnosis and monitor the arrhythmia (Snyder and Copel, 2005). Of all possible fetal arrhythmias, supraventricular tachycardia (SVT) and congenital heart block are serious. SVT may be treated in utero, whereas heart block is not treatable. Medical management of SVT consists of pharmacologic fetal cardioversion. The pharmacologic agents used are such drugs as digoxin, beta-blockers, procainamide, and quinidine.
Fetal Heart Rate Patterns and Periodic Rate Changes
FHR patterns express the mechanism of insult to the fetus. Knowing the mechanism facilitates appropriate nursing response and intervention. It also helps predict whether a change can be made and how long it might take. Periodic changes are in response to certain stimuli. When FHR accelerations are observed, they are usually explained by fetal movement or healthy response to contractions. The FHR can demonstrate patterns of acceleration or deceleration in response to most stimuli. Table 3-5 provides a summary of accelerations and decelerations. Table 3-6 describes sinusoidal pattern.
| Category I (Normal) Rate Changes | |
| Uniform Accelerations (Fig. 3-9, A) | |
| Description | Uniform shape |
| Begin when contraction begins and end when contraction ends | |
| Often mirror intensity of contractions | |
| Mechanism of insult | Sympathetic response to stimuli |
| Significance | Healthy CNS response |
| Often associated with breech presentations | |
| Nursing intervention | Totally benign, so none needed; document |
| Nonuniform Accelerations (Fig. 3-9, B) | |
| Description | Nonuniform in shape |
| Usually occur in response to fetal movement so they vary in contraction cycle | |
| Mechanism of insult | Sympathetic response to stimuli |
| Significance | Healthy CNS response; reassuring |
| Nursing intervention | None |
| Early Decelerations (Fig. 3-10, A) | |
| Description | Usually symmetric |
| Frequently mirror contraction intensity | |
| Onset, nadir, and recovery of the deceleration occur at the same time as the onset, highest point, and recovery of the contraction. | |
| Begin when contraction begins and end when contraction ends | |
| When noted, usually occur between 4- and 7-cm dilation of cervix, but can occur at any time | |
| Mechanism of insult | Head compression |
| Parasympathetic (vagal) reflex caused by pressure on fontanels against resisting cervix | |
| Significance | Considered normal, although they do not occur in all fetuses |
| Nursing interventions | Differentiate these from late decelerations |
| No action necessary or helpful; document | |
| Variable Decelerations | |
| Description | Variable in shape, often V- or W-shaped |
| Variable placement in relationship to contractions; may occur between or with contractions | |
| Heart rate falls abruptly (onset to the lowest point in <30 sec) and rises abruptly | |
| Decrease in the FHR is ≥15 bpm lasting ≥15 sec and <2 min in duration | |
| Defined as recurrent if they occur with ≥50% of uterine contractions in any 20-minute window | |
| Defined as intermittent if <50% in any 20-minute segment | |
| Mechanism of insult | Cord compression |
| Significance | Category II (indeterminate) if recurrent or with other characteristics such as a slow return to baseline or overshoots |
| Nursing intervention | Change maternal position |
| Category II (Indeterminate) and Category III (Abnormal) Rate Changes | |
| Variable Decelerations (Fig. 3-10, B) | |
| Significance | Category II (indeterminate) if: |
| Recurrent | |
| Followed by tachycardia | |
| Slow return to baseline | |
| “Overshoots” | |
| Category III (abnormal) if: | |
| Recurrent with absent baseline variability | |
| Nursing interventions | Turn side to side or to knee-chest position |
| Give O 2 at 8–10 L/min by tight face mask | |
| Improve circulating volume | |
| Expect expeditious delivery if Category III (abnormal) | |
| Document | |
| Late Decelerations (Fig. 3-10, C) | |
| Description | Usually symmetrical |
| Gradual decrease (onset to nadir ≥30 seconds) and return to baseline associated with a uterine contraction | |
| Nadir of the deceleration occurs after the peak of the contraction | |
| Generally the onset, nadir, and recovery of the deceleration occur after the beginning, peak, and ending of the contraction | |
| Description, cont’d | Defined as recurrent if they occur with ≥50% of uterine contractions in any 20-minute window |
| Defined as intermittent if <50% in any 20-minute segment | |
| Mechanism of insult | Uteroplacental insufficiency, leading to CNS hypoxia or myocardial depression |
| Significance | Always Category II (indeterminate) or III (abnormal) regardless of depth of deceleration |
| Acute episodes and moderate variability are more likely to be correctable | |
| Chronic episodes accompanied by decreased or absent variability are less likely to be correctable; usually associated with fetal acidosis | |
| Nursing interventions | Turn patient to side |
| Give O 2 at 8–10 L/min by tight face mask | |
| Rapidly infuse IV fluid | |
| Correct hypotension | |
| If oxytocin (Pitocin) used, turn it off | |
| Expect expeditious delivery if not corrected in 30 minutes; document | |
| Modified from American College of Obstetricians and Gynecologists (ACOG): Antepartum fetal surveillance, Practice Bulletin, No. 9, Washington, DC, 1999, ACOG; Association of Women’s Health, Obstetric, and Neonatal Nurses (AWHONN): Fetal heart monitoring: principles and practices, ed 4, Washington, DC, 2009, AWHONN. | |
| CNS, Central nervous system; IV, intravenous; O 2, oxygen. | |
| Prolonged Deceleration (Fig. 3-10, D) | |
| Description | Abrupt deceleration of at least 15 bpm, lasting 2–10 minutes |
| Mechanism of insult | Prolonged cord compression |
| Significance | If lasts longer than 10 minutes, fetus may become acidemic, followed by myocardial depression |
| Nursing interventions | Notify physician or midwife of first occurrence |
| Check for cord prolapse | |
| Turn patient side to side or to knee-chest position until change is affected | |
| Give O 2 at 8–10 L/min by tight face mask | |
| Correct maternal hypotension; increase IV fluids | |
| Continually observe until delivery; document | |
| Be prepared for emergency delivery | |
| CNS, central nervous system; FHR, fetal heart rate; IV, intravenous; O 2, oxygen. | |
| Description | Smooth, undulating baseline with regular (3–5) oscillations per minute that persists for ≥20 minutes |
|---|---|
| Mechanism of insult | Derangement of CNS control of FHR secondary to increased arginine vasopressin |
| When severe degree of hypoxia from fetal anemia is coupled with fetal hypovolemia | |
| Significance | Category III (abnormal) fetal heart rate finding |
| Only way to treat successfully in utero is by fetal intrauterine transfusion | |
| Nursing interventions | Prepare for emergent delivery |
| Prepare for intrauterine transfusion | |
| Position patient laterally | |
| Infuse IV fluids rapidly | |
| Give O 2 at 6–10 L/min by face mask; document | |
ANTEPARTUM AND INTRAPARTUM FETAL SURVEILLANCE
The latest census statistics estimate that more than two thirds of fetal deaths occur in the antepartum period (ACOG, 1999). Certainly a means of surveillance that allows detection of risk before damage occurs could greatly benefit those pregnancies. Antepartum monitoring provides a means of doing just that. When fetal compromise takes place, fetal activities are lost in reverse order of their development. FHR decelerations occur first, followed by loss of, in order, accelerations, breathing movements, body movements, and muscle tone, and then death occurs (Harman, 2009). Decreased amniotic fluid can also indicate fetal compromise because decreased renal blood flow lowers fetal urinary output, resulting in decreased amniotic fluid volume. Decreased amniotic fluid, on the other hand, can cause fetal compromise because of the increased risk for cord compression (ACOG, 1999).
In gestations less than 27 weeks, causes of intrauterine death have been identified to include infection, abruption, and lethal congenital abnormalities. And in gestations at greater than 28 weeks, causes identified may include growth restriction and placental abruption. However, 27% to 60% of intrauterine fetal deaths are unexplained (Shaffer and Parer, 2007).
The most common maternal conditions associated with fetal compromise follow:
• Intrauterine growth restriction
• Hypertensive disorders of pregnancy
• Chronic hypertension
• Diabetes
• Postterm pregnancy
• Connective tissue disease
• Renal disease
• Hemolytic incompatibility
• Multiple gestation
• Placental abnormalities
The purpose of testing is to identify the fetus at risk for decreased oxygenation resulting in permanent injury or death and to identify a healthy fetus and prevent unnecessary interventions (Tucker, Miller, and Miller, 2009). The decision as to when to begin antepartum testing may be based on multiple factors, including viability, severity of the condition, and when the condition is recognized. With the availability of regionalized centers, transportation capabilities, and long-distance telemetry, early detection of fetal compromise is possible and desirable for optimal treatment and outcome. The most frequently used tests to detect early fetal compromise are presented in Box 3-6, Box 3-7, Box 3-8, Box 3-9, Box 3-10, Box 3-11, Box 3-12 and Box 3-13, which may serve as useful guides for nursing policies and procedures (ACOG, 1999).
Box 3-6
Nonstress Test (NST)
Definition
An NST is a widely accepted method of evaluating fetal status by observing accelerations of the FHR following a stimulus such as fetal activity, indicating normal fetal pH and neurologic status.
Procedure
• Explain the testing procedure to the patient.
• Have the patient empty her bladder and then position herself in a semi-Fowler’s, lateral tilt position. Sitting or walking may stimulate fetal reactivity (Cito and others, 2005).
• Place the ultrasound transducer and tocotransducer.
• Document the date and time the test is started, the make and model of the monitor, the external modes used, the patient’s name, the reason for the test, and the maternal vital signs.
• Record maternal blood pressure at least once in 20 minutes.
• Run a 10- to 20-minute FHR contraction strip.
• If, at the end of the first 20 minutes, reactive criteria have not been met, consider vibroacoustic stimulation and then wait an additional 20 minutes for reaction that meets the criteria.
• At the end of the test, interpret and document the results and report them to the physician, midwife, or provider.
Interpretation
Reactive
• There are at least two accelerations of peak amplitude of at least 15 bpm above the baseline lasting 15 or more seconds within a 20-minute period. Other Category I (normal) features such as presence of variability and absence of Category II (indeterminate) periodic or episodic decelerations such as a prolonged deceleration or recurrent late decelerations with any spontaneous contractions or fetal movement are described and expected for a test to read as reactive (Fig. 3-12).
Nonreactive
• There are no accelerations over a 40-minute period or they fail to meet reactive criteria (Fig. 3-13).
Management
• A reactive NST should be repeated every 3 or 4 days for continued prediction of fetal well-being.
• If the NST remains nonreactive after the second 20 minutes or if any Category II periodic changes are present, another more definitive evaluation of the fetus, such as ultrasound for a biophysical profile, is indicated.
Advantages
• It is a noninvasive test requiring no initiation of contractions.
• It is quick to perform.
• There are no known side effects.
• It has a low false-negative rate (less than 1%) (ACOG, 1999).
Disadvantages
• It is not as sensitive to fetal oxygen reserves as CST.
• It has a high false-positive rate, 80% to 90% (ACOG, 1999).
CST, Contraction stress test;
FHR, fetal heart rate;
NST, nonstress test.
Box 3-7
Vibroacoustic Stimulation
Definition
A technique used to evaluate fetal status by observing accelerations of the FHR. Often used in conjunction with a nonstress test to elicit an acceleration indicating the absence of acidosis.
Vibroacoustic stimulation is an evaluation tool only used with a baseline rate that is within normal limits. If the fetus is experiencing a deceleration or bradycardia, vibroacoustic stimulation is not an appropriate intervention.
Harman (2009) states that vibroacoustic stimulation should not be part of routine testing in high risk pregnancies.
Procedure
• If no fetal movements are observed, use an acoustic stimulation device or an electrolarynx to produce a vibratory sound stimulus.
• Explain the testing procedure to the patient and the reasons for its use; assure her it is not harmful to the fetus.
• Apply stimulus to the maternal abdomen over the fetus’ head for 1 second; wait 1 minute.
• If no acceleration occurs after first stimulus, apply a second stimulus for 2 seconds; wait 1 minute.
• If no acceleration occurs after the second stimulus, apply a third stimulus for 3 seconds; wait 1 minute.
• Report results to the physician, midwife, or provider.
I nterpretation
Reactive
• Indicated by the presence of an acceleration. The peak of the acceleration must be equal to or greater than 15 bpm above the baseline and the acceleration must last equal to or greater than 15 seconds from the onset to the return to the baseline.
Advantages
• It decreases NST length (Tan and Smyth, 2003).
• It decreases the incidence of nonreactive NST (Tan and Smyth, 2003).
• There are no known risks if the protocol outlined is followed.
Additional Information
• Use of vibroacoustic stimulation for assessment of fetal wellbeing during labor in the presence of a nonreassuring FHR tracing is not supported by evidence in randomized controlled trials (East, Smyth, Leader, Henshall, Colditz, Tan, 2005).
FHR, Fetal heart rate;
NST, nonstress test.
Box 3-8
Fetal Movement Counting
Definition
Maternal perception of fetal body movement has been used as an indicator of fetal well-being. Animal studies have found a reduction in movements or the absence of movement in response to chronic hypoxia. Although there are no current human studies the principles have been applied to fetal behavior.
The goal of fetal movement counting is that when a mother identifies a decrease in her baby’s normal movement pattern she can report this to her healthcare giver and additional testing can be accomplished with the hopes of preventing fetal death.
Mangesi and Hofmeyr (2007) identified the lack of data to support the practice of fetal movement counting in preventing fetal death but agree there is not enough evidence to influence practice at this time.
Procedure
• Teach patient the significance of fetal movements.
• Teach patient a fetal assessment method—count fetal movements or record time.
• Count fetal movements for a fixed period of time. Instruct the patient to lie down on her side and count all the fetal movements felt in 1 hour.
• Record time taken to count a fixed number of fetal movements. Instruct the patient to start counting at 9 a.m. and stop counting for the day and record the time when 10 fetal movements have been noted.
• Demonstrate how to record movements on a daily fetal movement record.
Interpretation
• Report decreased fetal movement compared with the previous day’s counts or fewer than 10 fetal movements in any 1 hour period.
Management
• If decreased fetal movement is reported, evaluate fetal status with an NST or a biophysical profile immediately and manage according to the results.
Gestational Influences
• Gestational age: At 34 to 38 weeks fetal movements show a maturational decrease in number with the onset of typical infant behaviors of small-amplitude highly coordinated movements (Harman, 2009).
• Diurnal rhythm: Normally fetal movement is increased in the late evening.
Fetal Behavior
• State: Fetal behavioral states can be defined by the beginning of the third trimester. Other than rapid eye movements and repetitive mouthing movements there is usually no fetal movement during quiet sleep. In the middle of the 3rd trimester inactivity extends from about 220 seconds to as long as 110 minutes by 40 weeks (Harman, 2009).
• Drugs: Depressant drugs such as barbiturates, narcotics, and alcohol can reduce fetal movement. In therapeutic doses, most drugs do not reduce fetal movement.
• Fetal malformation: A fetus with a malformation is more likely to have reduced activity.
NST, Nonstress test.
Box 3-9
Contraction Stress Test
Definition
A CST is a fetal well-being test that is infrequently used to determine how the fetus responds to relative hypoxia during a contraction. A compromised fetus, with a limited ability to compensate for mild hypoxia because of limited oxygen reserves, demonstrates a consistent pattern of late decelerations during the test.
Procedure
• Explain the testing procedure to the patient.
• Have the patient empty her bladder and then position herself in a semi-Fowler’s position. A wedge may be placed under her hip to prevent supine hypotension if needed.
• Place the ultrasound transducer and tocotransducer.
• Document the date and time the test is started, make and model of monitor, the external modes used, the patient’s name, the reason for the test, and the maternal vital signs.
• Run a 20-minute NST for baseline information regarding FHR and uterine contractions.
• Stimulate contractions either by nipple stimulation of endogenous oxytocin or with intravenous oxytocin.
• Observe for uterine tachysystole.
• Assess maternal blood pressure every 10 to 15 minutes during the test and when the test is completed.
• Discontinue contraction stimulation when three or more contractions of more than 40 seconds duration within a 10-minute period occur.
• Interpret the test results and report findings to the provider.
• Continue monitoring until uterine and FHR activity have returned to prestimulation state.
Initiation of Contractions with Nipple Stimulation
• Have the patient begin, on one side, nipple brushing through clothing. Have her continue until a contraction begins or for 10 minutes.
• If no contraction occurs in 10 minutes of brushing, have her change sides and continue for 10 minutes. If still not effective, have her brush both nipples simultaneously.
• Have the patient continue nipple brushing on effective side or sides until a contraction occurs. Stop until the contraction is over, and then begin again until three contractions occur in 10 minutes.
Stimulation of Contractions with Oxytocin
• Start mainline intravenous normal saline or Ringer’s lactate.
• Piggyback oxytocin diluted so that increments of 0.5 mU/min can be delivered.
• Start at 0.5 mU/min; double amount every 15 to 20 minutes until 4 mU and then increase by 2 mU until three contractions occur in 10 minutes or maximum dose of 16 mU is reached.
Interpretation
Negative (Fig. 3-14)
• No decelerations are noted on the entire strip. Variability is present, and there is an absence of any Category I or Category II changes.
Equivocal
• A test may be equivocal for one of three reasons:
1. Suspicious: Less than 50% of the contractions on the entire strip have late decelerations: (Fig. 3-15,
A).
2. Tachysystole: A contraction frequency of more than five in 10 minutes, fewer than 60 seconds between contractions, or a contraction lasting longer than 90 seconds with a late deceleration occurring (Fig. 3-15,
B).
3. Unsatisfactory: The quality of the tracing is too poor to accurately interpret FHR with contractions; or the frequency of three contractions in 10 minutes cannot be obtained for an endpoint of the test (Fig. 3-15,
C).
Positive (Fig. 3-16)
• Fifty percent or more of the contractions on the strip have late decelerations associated with them even if the endpoint of three contractions in 10 minutes is not obtained.
Management
• A negative CST predicts continued fetal well-being for 7 days and needs only to be repeated weekly provided maternal well-being is the same (Freeman, Garite, and Nageotte, 2003).
• An equivocal CST should be followed with another form of fetal assessment.
• A positive CST necessitates more vigorous management. If variability is present and the fetus is mature by the proper dates and in a vertex position, a very carefully monitored induction can be attempted. If the fetus is immature, treating the maternal condition that might have precipitated the problem may be the best treatment to give the baby a chance.
• With a positive CST when variability is absent, delivery by an emergency cesarean is the only chance for optimal outcome for the baby regardless of maturity.
• Regardless of test results, if variable decelerations are noted, an amniotic fluid index is recommended.
Advantages
• It is more sensitive to fetal oxygen reserves than NST.
• It has a low false-negative rate (less than 1%) (ACOG, 1999).
Disadvantages
• CST is contraindicated in such high risk conditions as preterm labor and placenta previa.
• It must be administered in a birthing setting.
• It has a false-positive rate greater than 50% (ACOG, 1999).
CST, Contraction stress test;
FHR, fetal heart rate;
NST, nonstress test.
Box 3-10
Amniotic Fluid Volume
Definition
Amniotic fluid volume (AFV) is the evaluation of the quantity of amniotic fluid. Amniotic fluid is the result of fetal urine production. Adequate placental blood flow usually promotes adequate fetal renal blood flow and therefore adequate urine output. Thus amniotic fluid volume reflects long-term uteroplacental function.
Procedure
Scan and measure the depth of the largest cord-free pocket of amniotic fluid. Research supports the technique over amniotic fluid index (AFI) (Magann and others, 2007).
Interpretation
• Less than 2 cm: Oligohydramnios
• Indicates need for delivery or close maternal and fetal surveillance.
• 2 cm to 8 cm: Normal
• Greater than 8 cm: Polyhydramnios
AFI, amniotic fluid index;
AFV, amniotic fluid volume.
From Harman C: Assessment of fetal health. In Creasy R, Resnik R, Iams J, Lockwood C, Moore T, editors: Creasy and Resnik’s maternal-fetal medicine: principles and practice, ed 6, Philadelphia, 2009, Saunders.
Box 3-11
Biophysical Profile (BPP)
Definition
A biophysical profile is an evaluation of fetal well-being through the use of various reflex activities that are CNS-controlled and sensitive to hypoxia, as well as the fetal environment that can affect fetal well-being.
Procedure
Scan the abdomen and assess fetal tone, movements, breathing, fetal reactivity (cardiotocogram), and amniotic fluid.
Interpretation (Harman, 2009)
The biophysical activities that are the first to develop are the last to disappear when asphyxia occurs.
•
Fetal tone: One or more episodes of extension of a fetal extremity with return to flexion; and/or opening and closing of hand.
• Starts to function at 7.5 to 8.5 weeks of gestation
• Is abolished at a pH less than 7.0
•
Fetal movement: Four or more body or limb movements within 30 minutes
• Starts to function at 9 weeks of gestation
• Is abolished when the pH is between 7.1 and 7.2
•
Fetal breathing: Intermittent, multiple episodes of hiccups or rhythmic fetal breathing movements of at least 30 seconds duration in a 30 minute observation.
• Starts to function at approximately 20 to 21 weeks of gestation
• Is abolished at a pH of 7.2
•
Fetal reactivity—Computerized cardiotocography (CTG): Two or more FHR accelerations of at least 15 bpm for at least 15 seconds within 20 minutes
• Starts to function at 26 to 28 weeks of gestation
• Is abolished at a pH of less than 7.19
•
Amniotic fluid: Decreased amniotic fluid can be the result of chronic hypoxia or can cause hypoxia. Normal amniotic fluid is recognized as at least one cord-free vertical pocket of amniotic fluid greater than 2 cm (Harman, 2009).
Scoring
• Assign 0 or 2 points each for fetal tone, movements, breathing, reactivity (cardiotocogram), and amniotic fluid volume.
• A BPP of 8 to 10 is normal if amniotic fluid volume (AFV) is normal. The test needs be repeated in 3 to 4 days.
• A BPP of 6 is considered equivocal. The test should be repeated. A persistent score of 6 indicates delivery of a mature fetus; if fetus is immature repeat the test in 24 hours.
• A BPP score of 0 to 4 means delivery by obstetrically appropriate method.
• A BPP score of 0 to 2 means immediate delivery.
Oligohydramnios constitutes an abnormal biophysical assessment regardless of the overall score (Harman, 2009).
Advantages
• It permits conservative therapy and prevents premature intervention.
• BPP evaluates multiple fetal variables.
AFV, amniotic fluid volume;
BPP, biophysical profile;
CTG, computerized cardiotocography.
Box 3-12
Modified Biophysical Profile (Modified BPP)
Definition
A modified biophysical profile is an evaluation of fetal well-being. It combines the results of a nonstress test with an amniotic fluid volume. The NST is a short-term indicator of fetal hypoxemia and the AFV is an indicator or long-term placental function.
Interpretation (Shaffer & Parer, 2007)
• Normal: Reactive NST and AFV >5 cm and absence of variable or late decelerations
• Abnormal: any
one of the following:
• Nonreactive NST
• Variable or late decelerations
• AFV <5 cm
BPP, biophysical profile;
NST, nonstress test;
AFV, Amniotic fluid volume
Box 3-13
Doppler Flow Studies
Definition
Doppler flow studies are noninvasive methods for studying intrauterine environment, specifically the uteroplacental blood flow in the umbilical arteries. Doppler flow studies can facilitate the decision-making process regarding delivery time in pregnancies complicated by intrauterine growth restriction.
Procedure
• The nurse should help the patient position herself in a supine position and place a wedge under her right side to facilitate adequate blood flow and reduce maternal positional side effects.
• A pulsed Doppler device is positioned over the fetus. The umbilical artery blood flow is distinguished from other blood flow by its characteristic waveform.
• The directed blood flow within the umbilical arteries is calculated using the difference between the systolic and the diastolic flow. Measurements are averaged from at least five waveforms.
Interpretation
• Elevations of the systolic/diastolic (S/D) ratio above 3.0 are considered abnormal (Shaffer & Parer, 2007).
• Elevations of the S/D ratio are seen in hypertensive disorders of pregnancy, fetal growth restriction, or other causes of uteroplacental insufficiency.
Fetal Oxygen Saturation Monitoring with Fetal Pulse Oximetry Assessment During Labor
Simpson and Porter (2001) and Garite and colleagues (2000) described the benefits of taking fetal O
2 saturation measurements during labor and compared them with the benefits of EFM. In a few studies, assessing fetal status with fetal O
2 saturation measurements was found to be as accurate as with EFM. Fetal pulse oximetry added to cardiotocography showed reduced caesarean section rates for nonreassuring fetal status in a single trial, although no difference was found in the overall caesarean section rate or the mother’s or newborn’s health (East, Chau, and Colditz, 2004; Bloom and others, 2006).
In May 2000 the Food and Drug Administration approved fetal O
2 saturation after careful consideration of the results of a multicenter randomized clinical study (Garite and others, 2000). The system used a single-use disposable sensor that was inserted into the uterus via the cervix and rests against the fetal temple, cheek, or forehead and is held in place by the uterine wall. The sensor usually rotates and descends with the fetus as labor progresses, which can affect the availability of data. Its measurements are based on the same premise as pulse oximetry in that the major light sensors in the blood are oxyhemoglobin and deoxyhemoglobin.
The American College of Obstetricians and Gynecologists did not endorse this device because of the lack of data to support improvement in clinical outcomes when compared with the potential cost with the introduction of this technology (ACOG, 2001). In January of 2009 the manufacturer discontinued the support of the N400 fetal oximeter (J.C. Reichert, personal communication, February 26, 2009).
NURSING MANAGEMENT
Assessments
Antepartum
• Auscultate FHR with fetoscope or Doppler for 60 seconds and record at appropriate intervals. To identify an increase or decrease in the rate count for multiple consecutive periods of 6 seconds (multiply by 10).
• Explain to the patient the reasons for antepartum testing and the procedure.
• Discuss the significance of and the procedure for monitoring fetal movement at home on a daily basis. Teach the patient when to notify her health care provider.
• Reinforce the importance of follow-up care.
• Refer to case management and/or social services for financial concerns if the family is without health benefits.
Intrapartum
Low risk patients
• When the patient is admitted in labor, apply external EFM for 20 minutes. Then assess FHR by intermittent auscultation during and after contractions or by continuous fetal monitoring.
• Assess maternal blood pressure, pulse, and respirations every 1 to 2 hours before the onset of active labor and every hour during active labor.
• During latent phase of labor, assess and record FHR every 30 to 60 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
• During active labor, assess and record FHR every 15 to 30 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
• During second-stage labor, assess and record FHR every 5 to 15 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
High risk patients
• When the woman is admitted in labor, apply external EFM for 20 minutes. Continuous electronic fetal monitoring is recommended for patients with high risk conditions by ACOG (AWHONN, 2009).
• During latent-phase labor, assess and record FHR pattern every 30 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
• During active-phase labor, assess and record FHR pattern every 15 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
• During second-stage labor, assess and record FHR pattern every 5 minutes (American Academy of Pediatrics (AAP) and American College of Obstetricians and Gynecologists (ACOG), 2007 and Association of Women's Health, 2009).
• FHR pattern assessment should include baseline heart rate, variability, and presence or absence of accelerations and decelerations (AWHONN, 2009).
• Assess maternal blood pressure, pulse, and respirations every 1 to 2 hours before the onset of active labor and every hour in active labor.
• Assess maternal temperature every 1 to 4 hours, depending on the stage of labor and status of membranes.
Interventions
On identification of a Category II
(indeterminate) or Category III
(abnormal) FHR pattern: (1) reposition the patient laterally, turn her from side to side, or have her get in a hands-and-knees position or modified Trendelenburg position, depending on pattern and fetal response; (2) start and/or infuse IV fluids (lactated Ringer’s) rapidly; (3) discontinue labor stimulant if being administered or, if not, obtain an order for 0.25 mg subcutaneous terbutaline; (4) administer O
2 at 8 to 10 L/min by mask; (5) notify physician or midwife; and (6) vibroacoustic or fetal scalp stimulation to assess fetal response may be used as appropriate.
• Treat by position change, fluids, and medications such as terbutaline for cessation of contractions if intolerance to labor is detected and there are more than 15 to 30 minutes before delivery set up.
• Monitor maternal contractions every 30 minutes, and maintain a safe and effective labor pattern with maternal positioning (of choice and therapeutic), fluids, and comfort measures as appropriate (see Chapter 27 and Chapter 28).
• Record fetal and maternal responses to nursing interventions. Notify physician or midwife of any adverse effects on fetal response (American College of Obstetricians and Gynecologists (ACOG), 1999 and Association of Women's Health, 2009).
CONCLUSION
Assessment of fetal well-being throughout pregnancy and intrapartum is paramount to achieve an optimal perinatal outcome. Nurses need skill in fetal assessment to accurately assess, develop, implement, evaluate, and document effective care to promote optimal outcomes. As we continue to add to our knowledge base we will be better equipped to provide evidence-based care to the families we encounter.
BIBLIOGRAPHY
Electronic Fetal Monitoring
Alfirevic, Z.; Devane, D.; Gyte, G.M.,
Continuous cardiotocography (CTG) as a form of electronic fetal monitoring (EFM) for fetal assessment during labour,
Cochrane Database Syst Rev (
Issue 3) (
2006);
Art. No.: CD006066. DOI: 10.1002/14651858.
American Academy of Pediatrics (AAP); American College of Obstetricians and Gynecologists (ACOG),
Guidelines for perinatal care.
ed 6 (
2007)AAP/ACOG,
Elk Grove Village, IL.
American College of Obstetricians; Gynecologists (ACOG),
Antepartum fetal surveillance, Practice Bulletin.
(
1999)ACOG,
No. 9, Washington, DC.
American College of Obstetricians; Gynecologists (ACOG),
Intrapartum fetal heart rate monitoring: nomenclature, interpretation, and general management principles, Practice Bulletin.
(
2009)ACOG,
No. 106, Washington, DC.
Association of Women’s Health, Obstetric; Neonatal Nurses (AWHONN),
Fetal heart monitoring: principles and practices.
ed 4 (
2009)AWHONN,
Washington, DC.
Blackburn, S.T.,
Maternal, fetal, & neonatal physiology.
ed 3 (
2007)Saunders,
St Louis.
Centers for Disease Control and Prevention (CDC),
National vital statistics system: beyond 20/20 method of delivery (
2006);
Available at:http://www.cdc.gov..
Cunningham, F.; Leveno, K.; Bloom, S.; Hauth, J.; Rouse, D.; Spong, C.,
Williams obstetrics.
ed 23 (
2010)McGraw-Hill Medical,
New York.
Feinstein, N.; Sprague, A.; Trepanier, M.,
Fetal heart rate auscultation.
ed 2 (
2008)Association of Women‘s Health Obstetric and Neonatal Nurses.
Freeman, K.,
Problems with intrapartum fetal heart rate monitoring interpretation and patient management,
Obstet Gynecol 100 (4) (
2002) 813–826.
Freeman, R.; Garite, R.; Nageotte, M.,
Fetal heart rate monitoring.
ed 3 (
2003)Lippincott Williams & Wilkins,
Baltimore.
Haggerty, L.; Nuttall, R.,
Experienced obstetric nurses’ decision-making in fetal risk situations,
J Obstet Gynecol Neonatal Nurs 29 (5) (
2000) 480–490.
Hamilton, B.; Martin, J.; Ventura, S.,
Births: preliminary data for 2007,
Nat Vital Stat Report 57 (12) (
2009) 1–23;
Retrieved fromhttp://www.cdc.gov/nchs/data/nvsr/nvsr57/nvsr57_12.pdf..
Knox, G.E.; Simpson, K.R.; Garite, T.J.,
High reliability perinatal units: an approach to the prevention of patient injury and medical malpractice claims,
J Health Risk Manage 19 (2) (
1999) 24–32.
Kochanek, K.; Martin, J.,
Supplemental analyses of recent trends in infant mortality.
(
2005)National Center for Health Statistics (NCHS),
Hyattsville, MD.
MacDorman, M.; Mathews, T.J.,
Recent trends in infant mortality in the United States,
National Center for Health Statistics (NCHS) Data Brief (
October 2008).
Macones, G.A.; Hankins, G.D.; Spong, C.Y.; Hauth, J.; Moore, T.,
The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines,
J Obstet Gynecol Neonatal Nurs 112 (3) (
2008) 510–515.
Macones, G.A.; Hankins, G.D.; Spong, C.Y.; Hauth, J.; Moore, T.,
The 2008 National Institute of Child Health and Human Development workshop report on electronic fetal monitoring: update on definitions, interpretation, and research guidelines,
Obstet Gynecol 112 (3) (
2008) 661–666.
Magann, E.F.; Chauhan, S.P.; Doherty, D.A.; ,
and others,
The evidences for abandoning the amniotic fluid index in favor of the single deepest pocket,
Am J Perinatol 24 (2007) 549–555.
Mahlmeister, L.,
Legal implications of fetal heart assessment,
J Obstet Gynecol Neonatal Nurs 29 (5) (
2000) 517–526.
McKeon, L.M.; Cunningham, P.D.; J.S., Detty Oswaks,
Improving patient safety: patient focused, high-reliability team training,
J Nurs Care Qual 20 (5) (
2008) 1–7.
Meschia, G.,
Placental respiratory gas exchange and fetal oxygenation,
In: (Editors: Creasy, R.; Resnik, R.; Iams, J.; Lockwood, C.; Moore, T.)
Creasy and Resnik‘s maternal-fetal medicine: principles and practiceed 6 (
2009)Saunders,
Philadelphia.
Phelan, J.; Kim, J.,
Fetal heart rate observations in the brain-damaged infant,
Semin Perinatol 24 (3) (
2000) 221–229.
Radin, T.; Harmon, J.; Hanson, D.,
Nurses’ care during labor: its effect on the cesarean birth rate of healthy, nulliparous women,
Birth 20 (1) (
1993) 14–21.
Schmidt, J.,
The development of AWHONN’s fetal heart monitoring principles and practices workshop,
J Obstet Gynecol Neonatal Nurs 29 (5) (
2000) 509.
Simpson, K.,
Standardized language for electronic fetal heart monitoring,
MCN Am J Matern Child Nurs 29 (5) (
2004) 336.
Simpson, K.; Creehan, P.,
Perinatal nursing.
ed 3 (
2008)Lippincott,
Philadelphia.
Snyder C, Copel J: Fetal cardiac arrhythmias: diagnosis and therapy. In James D and others, editor:
High risk pregnancy: management options, ed 3, Philadelphia 2005 Saunders.
Society of Obstetricians and Gynecologists of Canada (SOGC),
Clinical practice guidelines: fetal health surveillance in labour No. 112 (2002).
Sweha, A.; Hacker, T.W.; Nuovo, J.,
Interpretation of the electronic fetal heart rate during labor,
Am Fam Physician 59 (9) (
1999) 2487–2500.
Thacker, S.B.; Stroup, D.; Chang, M.,
Continuous electronic heart rate monitoring for fetal assessment during labor,
Cochrane Database Syst Rev (
Issue 2) (
2001);
Art. No.: CD000063. DOI: 10.1002/14651858.CD000063.
Tucker, S.; Miller, L.A.; Miller, D.A.,
Mosby’s pocket guide to fetal monitoring: a multidisciplinary approach.
ed 6 (
2009)Mosby,
St Louis.
Antepartum Fetal Surveillance
American College of Obstetricians and Gynecologists (ACOG),
Antepartum fetal surveillance, Practice Bulletin.
(
1999)ACOG,
No. 9, Washington, DC.
Cito, G.; ,
and others,
Maternal position during non-stress test and fetal heart rate patterns,
Acta Obstet Gynecol Scand 84 (4) (
2005) 335–338.
Devoe, L.D.,
Antenatal fetal assessment: contraction stress test, nonstress test, vibroacoustic stimulation, amniotic fluid volume, biophysical profile, and modified biophysical profile—an overview,
Sem Perinatol 32 (4) (
2008) 247–252.
East CE, Smyth RMD, Leader LR, Henshall NE, Colditz PB, Tan KH: Vibroacoustic stimulation for fetal assessment in labour in the presence of a nonreassuring fetal heart rate trace,
Cochrane Database Syst Rev, (Issue 2), Art. No.: CD004664.
Freeman, R.; Garite, R.; Nageotte, M.,
Fetal heart rate monitoring.
ed 3 (
2003)Lippincott Williams & Wilkins,
Baltimore.
Harman, C.,
Assessment of fetal health,
In: (Editors: Creasy, R.; Resnik, R.; Iams, J.; Lockwood, C.; Moore, T.)
Creasy and Resnik‘s maternal-fetal medicine: principles and practiceed 6 (
2009)Saunders,
Philadelphia.
MacDorman, M.F.; Matthews, T.J.,
Recent trends in infant mortality in the United States.
NCHS data brief, No 9.
(
2008)National Center for Health Statistics,
Hyattsville, MD.
Mangesi, L.; Hofmeyr, G.J.,
Fetal movement counting for assessment of fetal well-being,
Cochrane Database Syst Rev (
Issue 1) (
2007);
Art. No.: CD004909. DOI: 10.1002/14651858..
Manning, F.,
Fetal biophysical profile: a critical appraisal,
Clin Obstet Gynecol 45 (9) (
2002) 975–985.
Shaffer, B.; Parer, J.,
Antepartum fetal monitoring,
In: (Editors: Queenan, J.; Spong, C.; Lockwood, C.)
Management of high-risk pregnancyed 5 (
2007)Blackwell,
Malden, MA.
Tan, K.H.; Smyth, R.M.D.,
Fetal vibroacoustic stimulation for facilitation of tests of fetal well being,
Cochrane Database Syst Rev (
Issue 4) (
2003);
Art. No.: CD002963..
United Health Foundation,
American Public Health Association (APHA), and Partnership for Prevention: America‘s health ranking.
(
2005)United Health Foundation,
Minnetonka, MN.
Wyatt, S.; Rhoads, S.,
A primer on antenatal testing for neonatal nurses: Part 2. Tests of fetal well-being,
Adv Neonatal Care 6 (5) (
2006) 228–241.
Fetal Oxygenation Saturation
American College of Obstetricians and Gynecologists (ACOG),
Fetal pulse oximetry, Committee Opinion, No. 258,
Obstet Gynecol 98 (3) (
2001) 523–524.
Bloom, S.L.; ,
and others,
Fetal pulse oximetry and cesarean delivery,
N Engl J Med 355 (21) (
2006) 2195–2202.
East, C.E.; Chan, F.Y.; Colditz, P.B.,
Fetal pulse oximetry for fetal assessment in labour,
Cochrane Database Syst Rev (
Issue 2) (
2004);
Art. No.: CD004075. DOI: 10.1002/14651858.CD004075. pub3.
Garite, T.; ,
and others,
A multicenter controlled trial of fetal pulse oximetry in the intrapartum management of non-reassuring fetal heart rate patterns,
Am J Obstet Gynecol 183 (5) (
2000) 1049–1058.
Simpson, K.; Porter, M.,
Fetal oxygen saturation monitoring: using this new technology for fetal assessment during labor,
AWHONN Lifelines 5 (2) (
2001) 26–33.