Description

Intermittent auscultation (IA) of the fetal heart rate may be performed non-electronically with a stethoscope, DeLee-Hillis fetoscope, or Pinard stethoscope, or electronically using a Doppler ultrasound (US) device (Figure 3-1). If using a stethoscope, the end should be turned to the domed, or bell, side rather than the flat side. The domed side is then placed on the maternal abdomen over the fetal back, which is the location where the fetal heart tones are heard the loudest. It is the ventricular fetal heart sounds that can be heard with the stethoscope and fetoscope. The fetoscope should be worn on the listener’s head, because bone conduction amplifies the fetal heart sounds for counting. The Doppler ultrasound device transmits ultra-high-frequency sound waves to the moving interface of the fetal heart valves and deflects these back to the device, converting them into an electronic signal that can be counted.^2,9,10 While auscultation with Doppler technology is most frequently performed transabdominally, a new transvaginal fetal Doppler probe is available. The device provides closer proximity to the uterus, enabling the detection of fetal heart tones (FHT) when difficult abdominally, as in obese patients and early gestations.

FIGURE 3-1 A. Auscultation of the FHR with a Pinard stethoscope. Vertex left occipitoanterior. B. 1, Ultrasound (US) fetoscope; 2, US stethoscope; 3, DeLee-Hillis fetoscope. C. 1, Echoheart transabdominal US transducer; 2, Echoheart transvaginal probe

(A. From Fraser DM, Cooper MA, editors: Myles textbook for midwives, ed 14, London, 2003, Churchill Livingstone. B. Courtesy Michael S. Clement, MD, Mesa, AZ. C. Courtesy EchoHeart, Inc., Damariscotta, ME.)

While electronic fetal monitoring is based on visual assessment, auscultation is an auditory assessment in which an instrument or device is used to count the number of fetal heartbeats occurring in a prescribed amount of time at specified intervals and in relation to uterine contractions. Clinicians must understand that IA is not simply electronic fetal monitoring without a tracing.^6,9 There are significant differences between IA and EFM.² These are summarized in Table 3-1.

TABLE 3-1 Fetal Heart Rate Characteristics Determined via Auscultation vs. Electronic FHR Monitor

In addition to serving as the primary method of fetal assessment in labor, auscultation technique can assist clinicians with differentiation of maternal heart rate (MHR) from fetal heart rate, and with correct placement of the external Doppler transducer used in EFM.

Procedure	Rationale
1. Perform Leopold’s maneuvers (Figure 3-2 FIGURE 3-2 Leopold’s Maneuvers. (From Lowdermilk DL, Perry SE, Cashion K, et al: Maternity & women’s health care, ed 10, St. Louis, 2012, Mosby.) ) by palpating the maternal abdomen.	1. To identify fetal presentation and position.
2. Apply ultrasound gel to device if using a Doppler ultrasound. Place the listening device over the fetal back. If using a fetoscope or stethoscope, firm pressure may be needed.	2. To obtain the clearest and loudest sound (easier to count).
3. Count the maternal radial pulse.	3. To differentiate MHR from FHR.
4. Palpate the abdomen for the presence or absence of uterine activity.	4. To be able to count FHR between contractions.
5. Count the FHR for 30 to 60 seconds after a uterine contraction.	5. To identify the auscultated baseline rate as well as changes in the rate (increases or decreases).
6. Also auscultate the FHR before, during, and after a contraction.	6. To identify the FHR during the contraction, as a response to the contraction and to assess for the absence or presence of increases or decreases in FHR.
7. When there are distinct discrepancies in FHR during listening periods, auscultate for a longer period during, after, and between contractions.	7. To identify significant changes that may indicate the need for electronic fetal monitoring (EFM).

Leopold’s maneuvers

Utilization and frequency of intermittent auscultation

Many countries prefer intermittent auscultation to continuous electronic fetal monitoring in women without risk factors, as this promotes their mobility, is less distracting, and provides a more natural birthing experience without the use of electronic devices. Reliance on the electronic monitor is more prevalent in the United States, most likely because of staffing patterns, staffing mix, and the increased use of defensive practices in a litigious environment. The American College of Obstetricians and Gynecologists³ suggests continuous monitoring for patients with high-risk conditions, noting the uncertainty regarding the safety of IA in high-risk pregnancies. Regardless of the method used to assess the fetal heart rate, the standard practice is to evaluate and record the heart rate at specific intervals.¹

The American College of Nurse-Midwives² reviewed references from the United States, Canada, and Great Britain regarding the frequency of auscultation for low-risk women and found fairly consistent recommendations for auscultation frequency of every 15 minutes in the active phase of the first stage of labor and every 5 minutes in the second stage. Nursing guidelines regarding the length and specific timing of auscultation are discussed in detail by the Association of Women’s Health, Obstetric and Neonatal Nurses (AWHONN).⁹

Documentation of auscultated fetal heart rate

Documentation of the auscultated fetal heart rate must be accompanied by other routine parameters that are assessed during labor, including uterine activity, maternal observations and assessment, and both maternal and fetal responses to interventions. It should be noted how long the fetal heart rate was auscultated and whether this was before, during, and/or immediately after a uterine contraction. The rate, rhythm, and abrupt or gradual increases or decreases of the fetal heart rate during any part of this auscultated period should be described in relationship to uterine activity.

Note: It is not appropriate to describe auscultated fetal heart rate using the descriptive terms associated with electronic fetal monitoring because the majority of the electronic fetal monitoring terms are visual descriptions of the patterns produced on the monitor tracing (e.g., early, late, and variable decelerations or variability). However, terms that are numerically defined, such as bradycardia and tachycardia, can be used.^2,6,9

Interpretation of auscultated fetal heart rate

Although the terms “reassuring” and “non-reassuring” are no longer used when electronic fetal monitoring is employed, they remain the commonly used summary terms for intermittent auscultation.⁹

Reassuring fetal heart rate characteristics

FHR with a normal baseline range of 110 to 160 beats per minute (bpm)

Regular rhythm (obtained between contractions), without wide fluctuations

Presence of increases from the baseline rate

Absence of decreases from the baseline rate

Nonreassuring fetal heart rate characteristics

A baseline FHR of <110 bpm (bradycardia) or >160 bpm (tachycardia)

Decreases in baseline FHR, with or without UA

Irregular rhythm

Management options for a nonreassuring FHR using intermittent auscultation include increasing the frequency of IA, implementation of intrauterine resuscitation techniques, application of EFM to clarify the FHR pattern visually, and nursing notification of the provider (midwife or physician).

Benefits and limitations of auscultation

Benefits

Widely available and easy to use

Less invasive

Outcomes comparable to EFM with 1:1 nursing care

Inexpensive

Comfortable for the woman

Provides freedom of movement for the woman

1:1 nursing care promotes “doula effect” benefits

Allows easy FHR assessment during use of hydrotherapy

Limitations

May be difficult to obtain the FHR in some situations, such as hydramnios and maternal obesity

Does not provide a permanent, documented visual record of the FHR

The counting of the FHR is intermittent

Cannot assess visual patterns of the FHR variability or periodic changes

Significant events may occur during periods when the FHR is not auscultated

May not allow early detection of the fetal heart rate changes that reflect hypoxemia

Not recommended for high-risk pregnancies

In summary, intermittent auscultation has been found to be effective if performed in a consistent manner by a clinician caring for a woman according to a prescribed frequency. Worldwide, auscultation is frequently and successfully employed as the first line of fetal assessment in low-risk populations. Nurses should be comfortable performing intermittent auscultation. Continued research regarding auscultation, especially research related to nurse/patient ratios and frequency of assessments in latent phase labor, could prove beneficial in the acceptance of auscultation in the United States.

Overview

Electronic fetal monitoring may be external or internal, or utilize a combination of both. The external mode employs the use of transducers placed on the maternal abdomen, to assess the fetal heart rate and uterine activity. The internal mode uses a spiral electrode (to assess the fetal heart rate) and an intrauterine pressure catheter (to assess uterine activity and intrauterine pressure). In some countries, electronic fetal monitoring is called cardiotocography or “CTG.” The following chart compares the external and internal modes of monitoring and gives a brief description of the equipment used for each.

Converting raw data into a visual display of FHR

The fetal heart rate data collected, whether by external or internal means, must then be converted into a visual display (Figures 3-3 and 3-4). This display may be on paper, a computer screen, or often both. Interpretation of electronic fetal heart rate monitoring is based on a visual assessment of data presented on a Cartesian graph. The gridlines on the horizontal (x) axis of the graph represent time in increments of 10 seconds. The gridlines on the vertical (y) axis represent the fetal heart rate in increments of 10 beats per minute. As illustrated in Figure 3-5, the fetal heart rate appears on the graph as an irregular horizontal line representing the fetal heart rate over a period of time.

FIGURE 3-3 Philips Avalon FM 50 fetal monitor provides measurement of the FHR including noninvasive triplet monitoring, FHR high/low audible and visual alarms, and FECG. Maternal parameters include toco and intrauterine pressure, blood pressure, pulse rate, pulse oximetry and ECG. It has cross-channel verification of maternal and fetal heart rate, displays FECG and MECG on the color display touch screen and has a LAN interface for compatibility with hospital IT networks.

(Courtesy Philips Medical Systems, Böblingen, Germany.)

FIGURE 3-4 Corometrics 250CX fetal monitor.

(Courtesy GE Healthcare, Milwaukee, WI.)

FIGURE 3-5 An FHR tracing has the appearance of an irregular horizontal line.

(Courtesy David A. Miller, MD.)

However, as demonstrated in Figure 3-6, closer inspection reveals that the “irregular horizontal line” is not a line at all. Instead, it is a series of individual, closely spaced points. Each point represents an individual heart rate that is calculated from the time between two successive heartbeats. This is a fundamental principle of electronic fetal heart rate monitoring and merits brief review.

FIGURE 3-6 Converting raw FHR data for visual display.

(Courtesy David A. Miller, MD.)

Fetal monitoring equipment used in clinical practice detects the fetal heartbeat in one of two ways. A fetal scalp electrode detects the actual electrical impulses that originate in the fetal heart and make up the fetal electrocardiogram. An external transducer uses Doppler ultrasound to detect cardiac motion. Regardless of the method of detecting the fetal heartbeat, the fetal heart rate monitor uses the same basic principles to process the raw data for visual display. If the fetal heart rate is derived from a direct fetal electrode detecting the fetal electrocardiogram, as illustrated in Figure 3-6, the monitor measures the distance between two successive R waves and calculates a heart rate based on that single R-R interval. The individual heart rate is plotted as a single point on the fetal heart rate graph. The monitor then measures the next R-R interval, calculates a new heart rate, and plots it as a new point on the graph. This process is repeated with every subsequent R wave. If the fetal heart rate is derived from an external Doppler ultrasound transducer, the monitor uses the peak of the Doppler waveform in place of the R wave and performs the same basic calculations. A normal fetal heart rate baseline rate of 140 beats per minute will yield approximately 140 individual graph points every minute, each representing an individual heart rate. To the eye, these individual points are spaced so closely together that they appear as a line. Variations in the fetal heart rate cause the line to appear irregular. The physiologic significance of these variations will be discussed in Chapter 5.

Ultrasound transducer

Description

An ultrasound transducer is a device that is placed on the maternal abdomen and generates high-frequency ultrasound waves that are transmitted into the tissues (Figure 3-7). As the ultrasound waves strike tissue interfaces, some of the waves are reflected back toward the transducer from which they originated. The transducer detects the returning waves and converts them into electric signals. When ultrasound waves are reflected from a moving interface, such as the fetal heart, the waves return at different frequencies. This phenomenon is known as the Doppler effect. The change in frequencies can be used to calculate the motion of the target. As described previously, Doppler-detected fetal heart motion is converted to a continuous graphic display of fetal heart rate printed on the upper portion of the fetal heart rate monitor strip. Simultaneously, the Doppler-detected fetal heart rate is converted electronically to an audible beep and flashing light on the monitor.

FIGURE 3-7 Placement of external transducers. The tocotransducer transmits UA. The US transducer transmits FHR.

(From Lowdermilk DL, Perry SE, Cashion K, et al: Maternity & women’s health care, ed 10, St. Louis, 2012, Mosby.)

The Doppler signal can be affected by changes in the position of the transducer or the fetus. Changes in the direction of the sound beam during contractions may cause a loss of signal and make the resulting tracing uninterpretable, and the transducer may need frequent repositioning due to maternal position changes. Artifact and erratic tracings may result from a number of causes, such as increased variability, halving or doubling of the fetal heart rate by the monitor, recording of maternal heart rate, fetal arrhythmias, and fetal or maternal movement.

Placement of ultrasound transducer

A sequential procedure with rationales is provided for the application of the ultrasound transducer.

Procedure	Rationale
1. Position the woman in a comfortable sitting or side-lying position.	1. To maximize uteroplacental blood flow by avoiding supine hypotension syndrome.
2. Perform Leopold’s maneuvers (see Figure 3-2).	2. To determine fetal position, lie, and presentation.
3. Align and insert the ultrasound transducer plug into the appropriate monitor port (labeled cardio, or US for ultrasound).	3. To provide connection without damaging connector pins (could result in a faulty signal).
4. Apply ultrasound gel to the underside of the transducer placed on the maternal abdomen.	4. To aid in the transmission of ultrasound waves.
5. Place the transducer on the abdomen, preferably over the fetal back, which is usually the point of maximum intensity.	5. To achieve the clearest signal.
6. Adjust the audio-volume control while moving the transducer over the abdomen.	6. To obtain the loudest audible fetal signal.
7. Count the maternal radial pulse and compare with fetal heart rate.	7. To differentiate between maternal and fetal heart rates.
8. Secure the ultrasound transducer with the abdominal belt or other fixation device.	8. To prevent displacement of the transducer.
9. Observe the signal-quality indicator.	9. To verify clarity of input based on correct placement of the transducer.
10. Set the recorder at a paper speed of 3 cm/min and observe the FHR on the monitor strip. Note: A speed of 1 or 2 cm/min is used in some countries.	10. To ensure that the paper feeds correctly and that the recording is clear.
11. Reposition the transducer whenever the fetal signal becomes unclear (e.g., when the woman moves or when the fetus descends in the pelvis).	11. To ensure a clear, interpretable tracing during fetal monitoring.
12. Carefully remove the transducer from the fixation device at the completion of monitoring, and cleanse the abdomen of gel.	12. To avoid damage to the transducer and remove accumulated gel from the abdomen.
13. Box 3-1 BOX 3-1 General Guidelines for Care, Cleaning, and Storage of External Transducers Exercise caution when removing and handling the US and tocotransducers so that they are not dropped or allowed to swing against any equipment, to protect from damage. Clean transducers according to the manufacturer’s operating manual, usually with a soft cloth using mild soap and water. Avoid submerging transducers or placing them beneath running water. Do not use alcohol or other cleaning solutions that may damage equipment. Gently and loosely coil cables for storage. Avoid tight coiling and sharp bending of the cables, which will result in damage to the wires or casing. Cables between monitor models and manufacturers are usually not interchangeable. Forced insertion into an incompatible monitor port is likely to result in damage. Dispose of disposable abdominal belts. Wash reusable belts according to the facility’s or the manufacturer’s suggested procedure before the next use. gives guidelines for care, cleaning, and storage of external transducers.	13. To prevent damage and ensure cleanliness of equipment.

Tocotransducer

Advantages and limitations of external transducers

Advantages

Noninvasive

Easy to apply

May be used during the antepartum period

May be used with telemetry

Does not require ruptured membranes or cervical dilation

No known risks to woman or fetus

Provides continuous recording of the fetal heart rate and uterine activity

Limitations

May limit maternal movement.

Frequent repositioning of transducers is often needed to maintain an accurate tracing.

US transducer (Doppler) may double-count a slow fetal heart rate of less than 60 bpm, resulting in an apparently normal fetal heart rate during a bradycardia; or it may half-count an elevated fetal heart rate of more than 180 bpm, resulting in an apparently normal fetal heart rate during a tachycardia.

Maternal heart rate may be counted if the ultrasound transducer is placed over the maternal arterial vessels, such as the aorta.

Tocotransducer provides information limited to frequency and duration of contractions; it cannot accurately assess strength or intensity of contractions.

Obese women may be difficult to monitor.

Preterm and/or multifetal gestations may be difficult to monitor.

Spiral electrode

Description

The spiral electrode monitors the fetal electrocardiogram from the presenting part. It is generally applied only after the membranes have been ruptured, although it may be applied through intact membranes when necessary.⁵ Additionally, the cervix must be sufficiently dilated to allow placement and the presenting part must be accessible and identifiable (Figure 3-8). Therefore the spiral electrode is used only during the intrapartum period.

FIGURE 3-8 Diagrammatic representation of internal mode of monitoring with intrauterine pressure catheter and spiral electrode attach to fetal scalp.

(From Lowdermilk DL, Perry SE, Cashion K, et al: Maternity & women’s health care, ed 10, St. Louis, 2012, Mosby.)

Contraindications

Planned application to the fetal face, fontanels, or genitalia

Inability to identify the portion of the fetus where application is contemplated

Presence or suspicion of placenta previa

Presence of active herpes lesions or human immunodeficiency virus

Maternal infection with hepatitis B or C

Situations requiring caution

Woman is positive for group B streptococcus, syphilis, or gonorrhea

The fetus is premature

It is important to refer to the manufacturer’s directions and guidelines, as well as current professional guidelines and institutional policies related to use of the fetal spiral electrode.

Intrauterine pressure catheter

Description

The intrauterine pressure catheter or transducer (IUPC) monitors contraction frequency, duration, intensity, and resting tone (Figure 3-9). A small catheter is introduced through the vagina transcervically into the uterus after the fetal membranes have been ruptured and the cervix is sufficiently dilated to identify the presenting part. The catheter is compressed during uterine contractions, placing pressure on a transducer. The pressure is then reflected on the monitor tracing in units of millimeters of mercury (mm Hg).

FIGURE 3-9 Intrauterine catheter with the sensor transducer located in the tip of the catheter provides uninterrupted UA monitoring. Saline-filled catheters are another type of catheter in use. Note that this catheter has an amnioport that may be used for amnioinfusion. The procedure of amnioinfusion is used to treat variable decelerations in the presence of oligohydramnios. See Appendix A for more information.

Intrauterine pressure catheters that have the pressure-sensing device within the catheter tip or cable do not require an instillation of sterile water for use. These catheters are provided with an amnioport to allow simultaneous amnioinfusion while monitoring uterine activity. Always refer to the manufacturer’s directions and guidelines, along with the facility’s policies and procedures, for information on use and insertion.

Advantages and limitations of internal monitoring

Advantages

Capability of accurately displaying some fetal cardiac arrhythmias when linked to ECG recorder

Accurately displays an FHR between 30 and 240 bpm

Only truly accurate measure of all UA (e.g., frequency, duration, intensity, and resting tone)

Allows for use of amnioinfusion

Positional changes do not usually affect quality of FHR tracing (may affect IUPC accuracy)

May be more comfortable than external transducer belt

Limitations

Presenting part must be accessible and identifiable to place fetal scalp electrode

Internal electrode may record maternal heart rate in presence of fetal demise

May not get good ECG conduction when excessive fetal hair is present

Requires (or will result in) rupture of membranes

Cervix must be dilated sufficiently to allow placement

Improper insertion can cause maternal or placental trauma

May increase risk for infection

A fetal monitoring equipment checklist (Table 3-2) can be used to check for and ensure proper functioning of the equipment. To allay any anxiety, the woman who is electronically monitored should be given an explanation of equipment operations and the possibility of need for adjustments during labor. The care given to the electronically monitored woman is the same as that given to any woman during labor, with the additional consideration of those factors that relate directly to the monitor.

TABLE 3-2 Fetal Monitoring Equipment Checklist

Name: Evaluator: ______________________________________________________________________

Date: ______________________________________

Items to Be CheckedYes No Remarks

Preparation of Monitor

1. Is the paper inserted correctly? (if using paper)

2. Is recording speed set appropriately? (3 cm/min in the U.S.; may use 1 cm/min or 2 cm/min outside the U.S.)

3. Are the transducer cables plugged securely into the appropriate port?

4. Was the monitor date/time verified (when using electronic documentation)?

Ultrasound (US) Transducer

1. Has US transmission gel been applied to the transducer?

2. Was the FHR tested and noted on the monitor strip?

3. Was the FHR compared to the maternal pulse and noted?

4. Does a signal light flash or an audible beep sound with each heartbeat?

5. Is the belt secure and snug but comfortable?

Tocotransducer

1. Is the tocotransducer firmly positioned where there is the least maternal tissue?

2. Has the tocotransducer been applied without gel or paste?

3. Was the UA reference depressed between contractions?

4. Is the belt secure and snug but comfortable?

Spiral Electrode

1. Is the spiral electrode attached to the presenting part of the fetus?

2. Is the connecter attached firmly to the electrode pad (on the leg plate or abdomen)?

3. Is the inner surface of the electrode pad pre-gelled or covered with electrode gel?

4. Is the electrode pad properly secured to the mother’s leg or abdomen?

IUPC

1. Is the length line on the catheter visible at the introitus?

2. Is it noted on the monitor paper that a test or calibration was done?

3. Has the monitor been set to zero according to the manufacturer’s directions?

4. Is the IUPC properly secured to the patient?

5. Is baseline resting tone of uterus documented?

Monitor tracing scale

The fetal heart rate and uterine activity are printed on scaled paper (Figure 3-11). The fetal heart rate is printed on the upper section and the uterine activity on the lower section. Monitors are preset by their manufacturers for the countries in which they are used. Note the differences in the range and scale of the fetal heart rate and uterine activity sections, as well as in the paper/recorder speed, in Figure 3-12. The monitor strip in Figure 3-12, A, depicts the tracing paper that is used with monitors used in North America, with a speed of 3 cm/min. The monitor strip in Figure 3-12, B, depicts the tracing paper that is used in many countries outside North America, with a speed of 1 cm/min. It is imperative to use tracing paper that is designed in the correct scale to match the monitor settings.

FIGURE 3-11 Fetal monitor display of FHR and UA. A, Monitor strip of external mode with ultrasound and toco as the signal source; B, Monitor strip of internal mode with spiral electrode and intrauterine catheter as the signal source.

FIGURE 3-12 A. Fetal monitor paper scale: 3 cm/min speed used in North America.

Vertical Axis
Heart Rate
Range	30 to 240 bpm
Scale	Increments of 10 bpm (30 bpm/cm)
Uterine Activity
Range	0 to 100 mm Hg pressure
Scale	Increments of 10 mm Hg
Horizontal Axis
Paper/recorder speed	3 cm/min = six 10-second subsections within 1 minute

B. Fetal monitor paper scale: 1 cm/min speed used in countries outside North America, with key points identified.

Vertical Axis
Heart Rate
Range	50 to 210 bpm
Scale	Increments of 5 bpm (20 bpm/cm)
Uterine Activity
Range	0 to 100 mm Hg pressure, or 0 to 13.3 kilopascal units (1 kPa = 7.5 mm Hg)
Scale	Increments of 10 mm Hg
Horizontal Axis
Paper/recorder speed	1 cm/min = 2 subsections (or 2 cm/min speed = four subsections)

Monitoring twins and multiples

Many monitors have the capability of monitoring twin or multiple gestations at the same time. Monitoring of twins may be done with two separate ultrasound transducers, or one fetus may be monitored by direct fetal scalp electrode (Figure 3-13). The dual tracings may be distinguished by a thicker or darker trace for one fetus and a thinner or lighter trace for the other fetus (Figure 3-14). Another option to distinguish the tracings between twins is a “twin offset” mechanism, which separates the two fetal heart rates on the tracing by a distance of about 20 beats per minute. Thus one twin appears to have a fetal heart rate that is higher than the actual heart rate. The manufacturer’s instruction manual should be consulted to have a clear understanding of this capability.

FIGURE 3-13 Monitoring of multiple gestations with separate US transducers. (Courtesy Philips Medical Systems, Böblingen, Germany.)

FIGURE 3-14 Dual US heart rate monitoring strip demonstrates the simultaneous external monitoring of twins.

(Courtesy GE Medical Systems Information Technologies, Milwaukee, WI.)

To clearly differentiate between twins, their positions in the uterus can be documented and ultrasound transducers labeled. The cross-channel verification alert may occur if both fetuses have the same/coincidental heart rates. If this occurs, relocate the tocotransducer(s) to detect the second fetal heart rate. In identifying twins or multiples, the fetus in the advanced position just above the cervix is labeled A, the next one B, and so on.

Artifact detection & signal coincidence with MHR

Fetal monitors have built-in artifact rejection systems, which are always in operation when using the external mode of fetal heart rate monitoring. Logic circuitry rejects data when there is a greater variation than is expected between successive fetal heartbeats. When repetitive variations vary by more than the accepted amount, newer monitors continue to print regardless of the extent of the excursion of the fetal heart rate. The older generation of monitors may switch from a hold mode to a non-record mode. The recorder resumes recording when the variations between successive beats fall within the predetermined parameters.

During internal monitoring, artifact is rare, and the logic system will miss only those changes that exceed the predetermined limits of the system. If there is an accessible switch to select a logic or no-logic mode, it is preferable to have the monitor in the no-logic mode when using the internal mode (spiral electrode) to detect fetal arrhythmias.

Signal coincidence with maternal heart rate can occur when using the external Doppler method, especially during second stage when MHR may become elevated during pushing. There are a number of case reports involving adverse fetal outcomes, including fetal demise in utero, which occurred following signal ambiguity where it was impossible to recognize the shift from the fetal heartbeat to maternal on the tracing printout¹⁵ (Figure 3-15).

FIGURE 3-16 The modified Toco transducer M2734B, `Toco MP,´ allows automatic maternal pulse detection and automatic coincidence detection via cross-channel verification that confirms both maternal and fetal signals.

(Courtesy Philips Medical Systems, Böblingen, Germany)

At the time of this writing, a new tocodynamometer has been developed by Philips that allows automatic maternal pulse detection and automatic coincidence detection using cross-channel verification, allowing confirmation of both maternal and fetal signals without use of maternal pulse oximetry or manual confirmation. (Figure 3-16).

FIGURE 3-15 A. Example of a FHR tracing showing maternal heart rate being recorded as fetal, note appearance of “accelerations” with maternal pushing efforts. B. Now FHR tracing shows both the actual fetal heart rate (upper tracing line) concomitantly with the maternal heart rate (lower tracing line). Maternal heart rate accelerations are seen with pushing efforts.

Telemetry

Remote internal or external fetal heart rate monitoring via radio wave telemetry (Figure 3-17) helps women remain ambulatory without the loss of continuous monitoring data. A woman may feel less confined, more relaxed, and more content if she can walk around. The transducer is worn by means of an abdominal belt or other device. Heart rate and uterine activity signals are continuously transmitted to a receiver that is connected to the fetal monitor. The monitor then processes and displays the data, and it prints the heart rate and uterine activity on the monitor strip. Use of a central display facilitates clinician surveillance of the telemetry-monitored patient.

FIGURE 3-17 A. The cordless transducer system (Avalon CTS) transmits information to a base station and prints fetal and uterine activity on a fetal monitor strip. Waterproof transducers may be used for the patient who is in bed, ambulating, or in the bath. B. Cordless US and tocotransducer are applied to the maternal abdomen for external monitoring.

(Courtesy Philips Medical Systems, Böblingen, Germany.)

In addition to standard ultrasound and tocotransducers, external watertight transducers are available. These can be used to continue fetal surveillance during hydrotherapy or waterbirth.

Troubleshooting the monitor

The electronic fetal monitor is a useful tool to assess fetal well-being. As with any electronic device, problems may occur, but they can often be overcome. A fetal monitoring equipment checklist (see Table 3-2) can be used to screen for appropriate application of the monitor. The following chart suggests actions for identified electro-mechanical problems.

Problem	Action
Power	Check power cord at wall and back of monitor.
Ultrasound
Half or double rate	Assess FHR with fetoscope, stethoscope, or Doppler.
	Check maternal pulse to rule out maternal signal, and document maternal pulse.
	Reapply ultrasound gel and recheck.
	Move transducer to search for a better signal.
	Consider applying spiral electrode.
Erratic trace or display	Reposition transducer.
	Reposition woman.
	Tighten ultrasound belt if too loose.
	Check gel on transducer (if it is dry, sound waves do not penetrate the skin). Reapply gel if needed. Move transducer if fetus is out of range.
Spiral electrode
Erratic trace or display	Check attachment pad on leg for adherence to skin.
	Ensure that connection of electrode is secure on attachment pad and that connector is securely inserted into the leg-plate cable.
Signal quality indicator is continuously red	Ensure that logic switch is off to assess for fetal arrhythmia.
	Apply a new spiral electrode.
Tocotransducer
Not recording	Check that cable is plugged into monitor and power is on
Numbers in high range	Readjust toco on abdomen; ensure that cable is fully attached to monitor.
	Zero monitor with toco/UA button between contractions, or replace with another toco.
Toco not picking up contractions	Palpate abdomen for best location to sense contractions, and reapply toco.
	Test toco by lightly depressing pressure transducer and observing readout on monitor.
	Tighten belt, or use another device to hold toco firmly against abdomen.
	Consider using intrauterine pressure catheter (IUPC).
Intrauterine pressure catheter
Not recording	Recheck cable insertion.
	Flush if using a fluid-filled catheter.
Resting tone (>25 mm Hg)	Palpate abdomen to identify uterine tonus before making equipment adjustments.
	Adjust level of strain gauge for fluid-filled catheters to maternal xyphoid.
	Zero or recalibrate non-fluid-filled catheter.
	Flush if using a fluid-filled catheter.
Not recording contractions	Check catheter markings at woman’s introitus (catheter may have slipped out).
	Replace catheter if necessary.
Elevated resting tone (hypertonus)	Higher resting tone may be noted with multiple gestation, uterine malformation or myoma, use of oxytocin, amnioinfusion, extraovular placement.
	Re-zero monitor.
	Replace catheter if incorrect placement.

Potential problems
Suspected fetal arrhythmia	Auscultate FHR with fetoscope or stethoscope. Perform fetal ECG.
Errors caused by incorrect paper speed or paper with different scale	Check annotation with paper speed: it should be 3 cm/min in North America.
	Check scale: it should be 30 to 240 bpm for FHR if paper speed is 3 cm/min, or 50 to 210 bpm if paper speed is 1 or 2 cm/min.
Cross-channel verification alert	Alert occurs with two coincidental heart rates. Verify maternal heart rate. Reposition ultrasound transducer(s) to detect second fetal heart rate.

Computerized perinatal data systems

Many institutions utilize computerized perinatal data systems that provide central surveillance, alerts, documentation, and archiving capabilities electronically. A central monitor display at the nurses’ station provides an opportunity to view tracings from several women at the same time (Figure 3-18), while single-screen displays of several women or of one woman can be accessed from remote locations, including the bedside, the staff locker room or lounge area, the physician’s office, or at home. Clinicians can have access to the monitor tracings from multiple patients and from a variety of locations. Perinatal data systems include the capability of real-time data entry in the form of detailed notes about examination results, cervical dilation, fetal station, administration of drugs, the woman’s position, and vital signs. Newer perinatal data systems offer universal electronic health records (EHRs) that incorporate the entire perinatal and neonatal spectrum, from prenatal care through delivery, as well as postpartum and neonatal care. Reports and “paper charts” can be generated with a printer linked to the display or shared electronically through the healthcare institution’s intranet.

FIGURE 3-18 Central display for EFM allowing access to multiple records in a variety of formats.

(Courtesy Philips Medical Systems, Böblingen, Germany.)

The majority of central display systems provide multiple options for accessing and viewing information (Figure 3-19), including the following:

A system status screen provides an instant overview of several beds on the system and indicates any alerts by room number. In addition, it can identify the signal source of any woman on the system.

A trend screen can provide the most recent few minutes of heart rate and UA data on any one woman, with immediate warning of critical conditions relating to any woman in the system.

Scrolling capabilities allow clinicians to review hours of FHR data in minutes, which can help identify changes over time, an important component of FHR tracing evaluation.

An alert screen can provide an immediate summary of the trend analysis on any woman. The data can be made available to the staff before, during, and after an alert.

FIGURE 3-19 Clinicians can review and print trending data, such as the history of maternal blood pressure readings, and quickly determine status changes.

(Courtesy GE Healthcare, Milwaukee, WI.)

The surveillance component of a perinatal data system can be set to alert for fetal tachycardia or bradycardia, signal loss, coincidental fetal and maternal heart rates, and other parameters. Ranges for the duration of, and recovery from, fetal bradycardia or tachycardia can be set at different levels for each patient. These systems are widely available from a variety of companies.

In addition to improving the quality of care through surveillance and alert capabilities, these systems provide database access for statistical reporting for administration, research, and quality purposes, especially when integrated with other hospital or outpatient information systems. This advance allows multiple data entry points across the continuum of care and serves to link care and services provided at different sites within the healthcare/hospital network.¹³ For example, if a woman presents to the birthing center in the middle of the night, the staff can readily access the entire antenatal record, the ultrasound report, nonstress test, and biophysical profile that were completed just the previous afternoon, even if performed at a different campus within the system. Additionally, some systems allow clinicians to access information and review fetal heart rate tracings using cellular phone displays (Figure 3-20).

FIGURE 3-20 Providers can access near real time FHR tracings and review patient data using their mobile phones. A. FHR tracing, including MHR. B. Patient listing.

(Courtesy AirStrip Technologies, Inc., San Antonio, TX.)

Electronic documentation on forms and flow sheets, together with annotated tracings and automated data acquisition of information such as maternal blood pressure and pulse, result in a complete and detailed electronic health record. The archival and retrieval of the original fetal monitoring tracings has proved to be a problem for most medical record departments because the process is labor intensive and the paper is space consuming and subject to deterioration. Microfiche records are less bulky to store but still take time to log, sort, and file in the medical record, although some facilities continue to do this. Computer-based electronic storage systems provide secure archival and retrieval options, and can help prevent loss or destruction of fetal monitoring data.

The ability to have multiple points of data entry, information retrieval, and reproduction of a woman’s record and fetal monitor tracing is a significant advancement. Coupled with an interface to the hospital admission, discharge, and other hospital-based information systems, it is contributing to the trend toward comprehensive, paperless, and fully electronic information systems.

Data-input devices

Electronic perinatal data systems may use a variety of data-input devices, including bar-code readers, keypads for data entry, light-pens (Figure 3-21), touch screens, remote event markers, and standard computer keyboards. The input is subsequently printed on the tracing (Figure 3-22). The use of these options can promote accurate documentation and help eliminate the need for handwritten annotations, which are sometimes illegible. Additionally, ongoing information important to documentation such as the time, date, paper speed, and signal source is routinely entered on the monitor strip automatically. For more on documentation and health information technology, see Chapter 10.

FIGURE 3-21 Data entry using drop-down menus and pen stylus for documentation directly on computer screen.

(Courtesy OBIX Perinatal System, Clinical Computer Systems, Inc., Elgin, IL.)

FIGURE 3-22 Documentation data is printed on monitor tracing.

(Courtesy OBIX Perinatal System, Clinical Computer Systems, Inc., Elgin, IL.)

Abdominal fECG and electromyogram (EMG)

Abdominal fECG is not new and was used as a standard monitoring modality in fetal monitors sold in the 1970s. But problems with reliability and advances in Doppler technology soon made Doppler ultrasound the standard external monitoring choice in the 1980s, and this has remained the norm in the United States. But as discussed earlier, Doppler technology continues to suffer from reliability problems, for two principal reasons: the separation of the fetal from the maternal heart rate, and the loss of signal during maternal position changes or fetal movement. In 2011, a new abdominal fECG monitor was introduced in the United States that offers solutions to these and other drawbacks of standard EFM.

The Monica AN24^® uses 5 electrodes placed on the pregnant abdomen to directly monitor the electrocardiogram from the fetal and maternal heart and the electromyogram (EMG) from the uterine muscle (Figure 3-23). Fetal and maternal heart rates and uterine activity are extracted within the device and transmitted wirelessly, via Bluetooth technology, to an interface device that allows the FHR data and uterine activity data to print or display on a standard commercial fetal monitor and central display¹⁴ (Figure 3-24).

FIGURE 3-23 A. Monica AN24 is a wireless and beltless device that can be used with existing monitors to obtain FHR via abdominal ECG. B. Electrodes placed on maternal abdomen monitor ECG from fetal and maternal heart, and the electromyogram (EMG) from the uterine muscle.

(Courtesy Monica Healthcare Ltd, Nottingham, UK.)

FIGURE 3-24 Monica AN24 docking station on top of Corometrics fetal monitor is connected via Monica IF24 Interface Device.

(Courtesy Monica Healthcare Ltd, Nottingham, UK and GE Medical System Information Technologies, Milwaukee, WI.)

The Monica AN24^® simultaneously monitors the electrophysiologic signals on three separate channels spanning the abdomen, following fetal movement changes and using a sophisticated method to uniquely identify the maternal ECG and subtract it from the signal leaving only the fetal ECG complex.^11,12 This eliminates much of the problem with fetal movement and signal interruption as well as maternal-fetal signal coincidence. Additionally, adipose tissue has less of an impact on the electrical signals monitored on the abdomen than it does on the transmission of ultrasound, so there is less signal loss in patients with elevated body mass indices (BMI).

The uterine activity is a reflection of the electromyogram (EMG), electrical activity produced by uterine muscle.¹² EMG data allows increased accuracy related to frequency, occurrence of peak, and duration over traditional pressure-sensitive toco transducers, but does not provide actual intensity measurement in mm Hg as with an intrauterine pressure catheter. Although clinicians will continue to assess contraction strength and uterine resting tone using palpation, the Monica AN24® eliminates the need for belts and frequent toco readjustments common in traditional monitoring. The wireless capabilities provide similar range to those seen with cell phone Bluetooth headsets, providing patient mobility of approximately 50 feet (15 meters) from the base, allowing for a variety of maternal activities during labor (Figure 3-25).

FIGURE 3-25 A, Woman sitting on birthing ball and B, woman ambulating, both wearing the Monica AN 24.

(Courtesy Monica Healthcare Ltd, Nottingham, UK.)

Benefits of the abdominal fECG and EMG approach include improved signal quality, elimination of maternal-fetal signal coincidence, and maternal mobility and comfort; however, the method cannot be used during hydrotherapy or waterbirth. While availability of the fetal ECG non-invasively is a clear benefit, there are some fetuses that generate a very poor fetal ECG as measured on the abdomen and cannot be monitored with this technology. Additionally, there are some limitations applicable only to the U.S. market, with FDA approval restricted to use in gestations of 36 completed weeks or greater, and lack of FDA approval for display of maternal heart rate (it is captured and separated from the fetal heart rate but not displayed). It should be noted that at time of this writing, approval for the display of maternal heart rate data was in process.

St segment analysis

When using internal fetal monitoring, clinicians may now access information regarding the ST segment of the fetal electrocardiogram during labor with an ST waveform analyzer (STAN®; Neoventa Medical, Göteborg, Sweden) that serves as an adjunct to standard EFM. Using a combination of strict FHR interpretation/management guidelines and ST waveform analysis, STAN® provides clinicians with information on the fetal myocardial response to hypoxia based on fetal electrocardiogram changes, specifically changes in the ST interval.^4,7,8,16

The STAN® system consists of a freestanding electronic fetal monitor with a special ST analysis feature (Figure 3-26). The monitor can be used with or without ST analysis, functioning as a standard fetal monitor with all gestational ages; however, use of the adjunctive ST analysis option requires several patient characteristics be met, which are as follows:

Planned vaginal delivery

>36 completed weeks of gestation

Singleton fetus

Vertex presentation

Ruptured amniotic membranes

FIGURE 3-26 The STAN® S31 fetal monitor, capable of both traditional EFM and adjunctive ST waveform analysis for selected patients has a 15-inch touch color display providing for a convenient review of traces.

(Courtesy Neoventa Medical, Mölndal, Sweden.)

Following appropriate patient selection, a special scalp electrode is applied (Figure 3-27) and fetal electrocardiogram data are analyzed to evaluate the T/QRS ratio and the ST interval (Figure 3-28). These data are evaluated and appear on the monitor screen below the electronic fetal monitoring tracing (Figure 3-29). Clinicians apply strict classification and analysis guidelines^4,7 to determine the fetal response to hypoxia and subsequent labor management. Further information on STAN® as an adjunct to electronic fetal monitoring, including clinical trials, is presented in Chapter 6.

FIGURE 3-27 Applied spiral scalp electrode and skin electrode.

(Courtesy Neoventa Medical, Mölndal, Sweden.)

FIGURE 3-28 FECG complex illustrating the relationship of various parameters evaluated by STAN®.

(Courtesy Neoventa Medical, Mölndal, Sweden.)

FIGURE 3-29 Computer screen showing EFM tracing (upper graph) and UA tracing on lower graph.

(Courtesy Neoventa Medical, Mölndal, Sweden.)