22: Physiologic and behavioral adaptations of the newborn

Initiation of breathing

During intrauterine life, oxygenation of the fetus occurs through transplacental gas exchange. At birth, the lungs must be established as the site of gas exchange. In utero, fetal blood was shunted away from the lungs, but when birth occurs the pulmonary vasculature must be fully perfused for this purpose. Clamping the umbilical cord causes a rise in blood pressure (BP), which increases circulation and lung perfusion.

There is no single trigger for newborn respiratory function. The initiation of respirations in the neonate is the result of a combination of chemical, mechanical, thermal, and sensory factors (Blackburn, 2018).

Signs of respiratory distress

Signs of respiratory distress can include nasal flaring, intercostal or subcostal retractions (in-drawing of tissue between the ribs or below the rib cage), or grunting with respirations. Suprasternal or subclavicular retractions with stridor or gasping most often represent an upper airway obstruction. Seesaw or paradoxic respirations (exaggerated rise in abdomen with respiration as the chest falls) instead of abdominal respirations are abnormal and should be reported. A respiratory rate of less than 30 or greater than 60 breaths/min with the infant at rest must be evaluated. The respiratory rate of the infant can be slowed, depressed, or absent as a result of the effects of analgesics or anesthetics administered to the mother during labor and birth. Apneic episodes can be related to events such as rapid increase in body temperature, hypothermia, hypoglycemia, or sepsis. Tachypnea can result from inadequate clearance of lung fluid, or it can be an indication of respiratory distress syndrome (RDS). Tachypnea can be the first sign of respiratory, cardiac, metabolic, or infectious illnesses (Gardner, Enzman-Hines, & Nyp, 2021).

Changes in the infant’s color can indicate respiratory distress. Normally, within the first 3 to 5 minutes after birth, the newborn’s color changes from blue to pink. Acrocyanosis, the bluish discoloration of hands and feet, is a normal finding in the first 24 hours after birth (Fig. 22.1). Transient periods of duskiness while crying are common immediately after birth; however, central cyanosis is abnormal and signifies hypoxemia. With central cyanosis, the lips and mucous membranes are bluish (circumoral cyanosis). It can be the result of inadequate delivery of oxygen to the alveoli, poor perfusion of the lungs that inhibits gas exchange, or cardiac dysfunction. Because central cyanosis is a late sign of distress, newborns usually have significant hypoxemia when cyanosis appears.

Infants who experience mild TTN often have signs of respiratory distress during the first 1 to 2 hours after birth as they transition to extrauterine life. Tachypnea with rates up to 100 breaths/min can be present along with intermittent grunting, nasal flaring, and mild retractions. Supplemental oxygen may be needed. TTN usually resolves in 48 to 72 hours (Blackburn, 2018).

In neonates with more serious respiratory problems, symptoms of distress are more pronounced and tend to last beyond the first 2 hours after birth. Respiratory rates can exceed 120 breaths/min. Moderate to severe retractions, grunting, pallor, and central cyanosis can occur. The respiratory symptoms can be accompanied by hypotension, temperature instability, hypoglycemia, acidosis, and signs of cardiac problems. Common respiratory complications affecting neonates include RDS, meconium aspiration, pneumonia, and persistent pulmonary hypertension of the newborn (PPHN). Congenital defects such as anomalies of the great vessels, diaphragmatic hernia, or chest wall defects can cause severe respiratory problems. Blood incompatibilities such as hydrops fetalis can result in respiratory compromise (Gardner et al., 2021) (see Chapter 25).

Heart rate and sounds

The heart rate for a term newborn ranges from 120 to 160 beats/min, with brief fluctuations greater and less than these values usually noted during sleeping and waking states. The range of the heart rate in the term infant is approximately 80 to 100 beats/min during deep sleep and can increase to 180 beats/min or higher when the infant cries. A heart rate that is either high (more than 160 beats/min) or low (fewer than 100 beats/min) should be reevaluated within 30 minutes to 1 hour or when the activity of the infant changes.

The apical impulse (point of maximal impulse [PMI]) in the newborn is at the fourth intercostal space and to the left of the midclavicular line. The PMI is often visible and easily palpable because of the thin chest wall; this is also called precordial activity.

Irregular heart rate or sinus dysrhythmia is common in the first few hours of life but thereafter may need to be evaluated. Heart sounds during the neonatal period are of higher pitch, shorter duration, and greater intensity than during adult life. The first sound (S₁) is typically louder and duller than the second sound (S₂), which is sharp. The third and fourth heart sounds are not audible in newborns. Most heart murmurs heard during the neonatal period have no pathologic significance, and more than one-half of the murmurs disappear by 6 months of age. However, the presence of a murmur and accompanying signs such as poor feeding, apnea, cyanosis, or pallor is considered abnormal and should be investigated. There can be significant cardiac defects without a murmur or other symptoms. This reinforces the importance of ongoing assessment.

Blood pressure

The primary factors affecting BP are gestational age, postconceptional age, and birth weight (Flynn, 2021). BP values rise as these variables increase. Cuff size, state of alertness, and movement also affect BP measurement. Nurses and health care providers can compare infant BP measurements with available nomograms and tables to determine if values are within expected parameters. The mean arterial pressure (MAP) should be nearly equivalent to the weeks of gestation. For example, an infant born at 40 weeks of gestation should have a MAP of at least 40. The BP increases predictably over the first 5 days of life and then levels off, with minor variations noted during the first month of life. A drop in systolic BP (approximately 15 mm Hg) in the first hour of life is common. Expected values for BP (systolic/diastolic) in a term infant are:

(Moses, 2020)

Blood volume

Blood volume in the term newborn ranges from 80 to 100 mL/kg of body weight. In the preterm infant, the range is 90 to 105 mL/kg (Diehl-Jones & Fraser, 2021). The preterm infant has a relatively greater blood volume than the term newborn. This occurs because the preterm infant has a proportionately greater plasma volume, not a greater red blood cell (RBC) mass.

Delayed clamping of the umbilical cord changes the circulatory dynamics of the newborn. Delayed cord clamping (DCC) expands the blood volume from the so-called placental transfusion of blood to the newborn by as much as 100 mL, depending on the length of time to cord clamping and cutting. DCC has been associated with increased blood volume and BP and reduced risk for intraventricular hemorrhage and necrotizing enterocolitis. These benefits are most important for preterm infants. Polycythemia that occurs with delayed clamping is usually not harmful, although there can be an increased risk for hyperbilirubinemia that requires phototherapy. The American College of Obstetricians and Gynecologists (ACOG) recommends delayed cord clamping for at least 30 to 60 seconds for term and preterm infants unless there is a specific need for immediate clamping due to neonatal or maternal factors (ACOG, 2020) (see Chapter 16).

Signs of cardiovascular problems

Variations in vital signs can be indicative of cardiovascular problems. Persistent tachycardia (more than 160 beats/min) can be associated with anemia, hypovolemia, hyperthermia, or sepsis. Persistent bradycardia (less than 80 beats/min) can be a sign of a congenital heart block or hypoxemia. Unequal or absent pulses, bounding pulses, and decreased or elevated BP can indicate cardiovascular problems.

The newborn’s skin color can reflect cardiovascular problems. Pallor in the immediate postbirth period is often a sign of underlying problems such as anemia or marked peripheral vasoconstriction as a result of intrapartum asphyxia or sepsis. Cyanosis other than in the hands or feet, with or without increased work of breathing, can indicate respiratory and/or cardiac problems. The presence of jaundice can indicate ABO or Rh factor incompatibility problems (see Chapter 25).

Congenital heart defects are the most common types of congenital malformations (Centers for Disease Control and Prevention [CDC], 2020) (see Chapter 25). Although the more serious defects such as tetralogy of Fallot are likely to have clinical manifestations such as cyanosis, dyspnea, and hypoxia, others such as small ventricular septal defects can be asymptomatic. The prenatal history can provide information regarding risk factors for congenital heart defects, alerting the nurse to observe for symptoms. Maternal illness such as rubella, metabolic disease such as diabetes, and maternal drug ingestion are associated with an increased risk for cardiac defects.

Red blood cells

Because fetal circulation is less efficient at oxygen exchange than the lungs, the fetus needs additional RBCs for transport of oxygen in utero. At birth the average levels of RBCs, hemoglobin, and hematocrit are higher than those in the adult; these levels fall slowly over the first month. At birth, the RBC count ranges from 4.6 to 5.2 million/mm³ (Blackburn, 2018). The term newborn can have a hemoglobin concentration of 14 to 24 g/dL at birth, decreasing gradually to 12 to 20 g/dL during the first 2 weeks (Pagana, Pagana, & Pagana, 2019). Hematocrit at birth ranges from 51% to 56%, increases slightly in the first few hours or days as fluid shifts from intravascular to interstitial spaces (Blackburn), and by 8 weeks is between 39% and 59% (Pagana et al.). Polycythemia (central venous hematocrit greater than 65%) can occur in term and preterm infants as a result of DCC, maternal hypertension or diabetes, or intrauterine growth restriction.

The source of the sample is a significant factor in levels of RBCs, hemoglobin, and hematocrit. Capillary blood yields higher values than venous blood.

The timing of blood sampling is also significant; the slight rise in RBCs after birth is followed by a substantial drop. At birth the infant’s blood contains an average of 70% to 80% fetal hemoglobin; however, because of the shorter life span of the cells containing fetal hemoglobin, the percentage falls rapidly, so that by the age of 6 to 12 months, levels of fetal hemoglobin are less than 2% of the total hemoglobin (Chou, 2020). Iron stores generally are sufficient to sustain normal RBC production for approximately 4 months in the term infant, at which time a transient physiologic anemia can occur.

Leukocytes

Leukocytosis, with a white blood cell (WBC) count ranging from 9000 to 30,000/mm³, is normal at birth (Pagana et al., 2019). The number of WBCs increases up to 24,000/mm³ during the first day after birth. The initial high WBC count of the newborn decreases rapidly, and a stable level of 12,000/mm³ is normally maintained during the neonatal period (Blackburn, 2018). Newborns are susceptible to infection. Leukocytes, especially the polymorphonuclear neutrophils, are limited in their ability to recognize foreign protein and localize and fight infection early in life (Benjamin & Maheshwari, 2020). Sepsis can be accompanied by a corresponding rise in neutrophils; however, some infants initially have clinical signs of sepsis without a significant elevation in WBCs.

Platelets

Platelets appear to be activated during the birth process and demonstrate improved aggregation in the first hours after birth. The platelet count ranges between 150,000 and 300,000/mm³ and is essentially the same in newborns as in adults. Levels of vitamin K-dependent clotting factors II, VII, IX, and X at birth are about 50% of adult levels and increase slowly after birth. Levels of factors V, VIII, and XIII at birth resemble adult ranges (Letterio, Pateva, Petrosiute, et al., 2020).

Blood groups

The infant’s blood group is determined genetically and established early in fetal life. However, during the neonatal period the strength of the agglutinogens present in the RBC membrane gradually increases. Cord blood samples can be used to identify the infant’s blood type and Rh status.

Heat loss

The body temperature of newborn infants depends on the heat transfer between the infant and the external environment. Factors that influence heat loss to the environment include the temperature and humidity of the air, the flow and velocity of the air, and the temperature of surfaces in contact with and around the infant. The goal of care is to provide a neutral thermal environment for the newborn in which heat balance is maintained. The neutral thermal environment is the ideal environmental temperature that allows the newborn to maintain a normal body temperature to minimize oxygen and glucose consumption. Heat loss in the newborn occurs by four modes:

Heat loss must be controlled to protect the infant. Control of such modes of heat loss is the basis of caregiving policies and techniques. Drying the infant quickly after birth is essential to prevent hypothermia. Skin-to-skin contact with the mother is an effective means of reducing conductive and radiant heat loss and enhancing newborn temperature control and maternal-infant interaction. The naked newborn is placed on the mother’s bare chest and covered with a warm blanket; a cap may be placed on the infant’s head to help conserve heat (Fig. 22.2). Alternatively, the neonate is placed under a radiant warmer to reduce heat loss and promote thermoregulation.

Thermogenesis

In response to cold, the neonate attempts to generate heat (thermogenesis) by increasing muscle activity. Cold infants may cry and appear restless. Because of vasoconstriction the skin can feel cool to touch, and acrocyanosis can be present. There is an increase in cellular metabolic activity, primarily in the brain, heart, and liver; this also increases oxygen and glucose consumption.

In an effort to conserve heat, term newborns assume a position of flexion that helps to guard against heat loss because it diminishes the amount of body surface exposed to the environment. Infants also can reduce the loss of internal heat through the body surface by constricting peripheral blood vessels.

Adults are able to produce heat through shivering; however, the shivering mechanism of heat production is rarely operable in the newborn unless there is prolonged cold exposure (Blackburn, 2018). Newborns produce heat through nonshivering thermogenesis, triggered when the skin temperature decreases to less than 95°F to 96.8°F (35°C to 36°C). This is accomplished primarily by metabolism of brown fat, which is unique to the newborn; and secondarily by increased metabolic activity in the brain, heart, and liver. Brown fat is located in superficial deposits in the interscapular region and axillae and in deep deposits at the thoracic inlet, along the vertebral column, and around the kidneys (Fig. 22.3). Brown fat has a richer vascular and nerve supply than ordinary fat. Heat produced by intense lipid metabolic activity in brown fat can warm the newborn by increasing heat production as much as 100%. Reserves of brown fat, usually present for several weeks after birth, are rapidly depleted with cold stress. The amount of brown fat reserve increases with the weeks of gestation. A full-term newborn has greater stores than a preterm infant (Brand & Shippey, 2021).

Hypothermia and cold stress

When the neonate’s temperature drops, in response to norepinephrine release, vasoconstriction occurs as a mechanism to conserve heat. The infant can appear pale and mottled; the skin feels cool, especially on the extremities. If the hypothermia is not corrected, it will progress to cold stress, which imposes metabolic and physiologic demands on all infants, regardless of gestational age and condition. The respiratory rate increases in response to the increased need for oxygen. In the cold-stressed infant, oxygen consumption and energy are diverted from maintaining normal brain and cardiac function and growth to thermogenesis for survival. If the infant cannot maintain an adequate oxygen tension, pulmonary vasoconstriction follows and jeopardizes pulmonary perfusion. As a consequence, the Po₂ is decreased and the blood pH drops. Surfactant synthesis can be altered. These changes can prompt a transient respiratory distress or aggravate existing RDS. Moreover, decreased pulmonary perfusion and oxygen tension can maintain or reopen the right-to-left shunt across the ductus arteriosus.

The basal metabolic rate increases with cold stress. If cold stress is protracted, anaerobic glycolysis occurs, resulting in increased production of acids. Metabolic acidosis develops, and, if a defect in respiratory function is present, respiratory acidosis also develops (Fig. 22.4). Excessive fatty acids can displace the bilirubin from the albumin-binding sites and exacerbate hyperbilirubinemia. Hypoglycemia is another metabolic consequence of cold stress. The process of anaerobic glycolysis can deplete existing stores. If the infant is sufficiently stressed and low glucose stores are not replaced, hypoglycemia, which can be asymptomatic in the newborn, can develop (Gardner & Cammack, 2021).

Hyperthermia

Although less frequently than hypothermia, hyperthermia can occur and must be corrected. A body temperature greater than 37.5°C (99.5°F) is considered to be abnormally high and is typically caused by excess heat production related to sepsis or a decrease in heat loss. Hyperthermia can result from the inappropriate use of external heat sources such as radiant warmers, phototherapy, sunlight, increased environmental temperature, and the use of excessive clothing or blankets. The clinical appearance of the infant who is hyperthermic often indicates the causative mechanism. Infants who are overheated because of environmental factors such as being swaddled in too many blankets exhibit signs of heat-losing mechanisms: skin vessels dilate, skin appears flushed, hands and feet are warm to touch, and the infant assumes a posture of extension. The newborn who is hyperthermic because of sepsis appears stressed: vessels in the skin are constricted, color is pale, and hands and feet are cool. Hyperthermia develops more rapidly in a newborn than in an adult because of the relatively larger surface area of an infant. Sweat glands do not function well. Hyperthermia can cause neurologic injury and increased risk for seizures; severe cases can result in heat stroke and death (Brand & Shippey, 2021; Gardner & Cammack, 2021).

Fluid and electrolyte balance

In the term neonate, approximately 75% of body weight consists of total body water (extracellular and intracellular). A reduction in extracellular fluid occurs with diuresis during the first few days after birth. The weight loss experienced by most newborns during the first few days after birth is caused primarily by extracellular water loss (Dell, 2020).

The daily fluid requirement for neonates weighing more than 1500 g is 60 to 80 mL/kg during the first 2 days of life. From 3 to 7 days the requirement is 100 to 150 mL/kg/day, and from 8 to 30 days it is 120 to 180 mL/kg/day (Dell, 2020).

At birth, the glomerular filtration rate (GFR) of a newborn is significantly lower than in the adult. This results in a decreased ability to remove nitrogenous and other waste products from the blood. The GFR rapidly increases during the 2 to 4 weeks after birth as a result of postnatal physiologic changes, including decreased renal vascular resistance, increased renal blood flow, and increased filtration pressure. The GFR gradually rises to adult levels by 2 years of age (Blackburn, 2018; Vogt & Springel, 2020).

Sodium reabsorption is decreased as a result of a lowered sodium- or potassium-activated adenosine triphosphatase activity. The decreased ability to excrete excess sodium results in hypotonic urine compared with plasma, leading to a higher concentration of sodium, phosphates, chloride, and organic acids and a lower concentration of bicarbonate ions.

Tubular reabsorption of glucose in the term neonate is similar to that of an adult. Although the renal threshold for glucose is lower, newborns do not typically exhibit glycosuria.

Because of a lower renal threshold for bicarbonate and a limited capacity for reabsorption, the neonate’s serum bicarbonate and plasma pH levels are lower. Buffering capacity is decreased. This reduces the newborn’s ability to cope with events (e.g., cold stress) that produce acidosis (Blackburn, 2018).

Signs of renal system problems

The renal system has a wide range of functions. Dysfunction resulting from physiologic abnormalities can range from the lack of a steady stream of urine to gross anomalies such as hypospadias and exstrophy of the bladder, which can be identified easily at birth. Enlarged or cystic kidneys can be identified as masses during abdominal palpation. Some kidney anomalies also can be detected by ultrasound examination during pregnancy (see Chapter 25).

Digestion

The infant’s ability to digest carbohydrates, fats, and proteins is regulated by the presence of certain enzymes. Most of these enzymes are functional at birth except for pancreatic amylase and lipase. Amylase is produced by the salivary glands after approximately 3 months of age and by the pancreas at approximately 6 months of age. This enzyme is necessary to convert starch into maltose and occurs in high amounts in colostrum. The other exception is lipase, also secreted by the pancreas; it is necessary for the digestion of fat. The normal newborn is capable of digesting simple carbohydrates and proteins but has a limited ability to digest fats. Mammary lipase in human milk aids in digestion of fats by the neonate.

Lactase levels in newborns are higher than in older infants. This enzyme is necessary for digestion of lactose, the major carbohydrate in human milk and commercial infant formula.

Stools

Meconium fills the lower intestine at birth. It is formed during fetal life from the amniotic fluid and its constituents, intestinal secretions (including bilirubin), and cells (shed from the mucosa). Meconium is greenish black and viscous and contains occult blood. Most healthy term infants pass meconium within the first 12 to 24 hours of life, and almost all do so by 48 hours (Fig. 22.5). The number of stools passed varies during the first week, being most numerous between the third and sixth days. Newborns fed early pass stools sooner. The colostrum consumed by breastfed neonates during the first 2 to 3 days after birth promotes stooling. Progressive changes in the stooling pattern indicate a properly functioning GI tract (Box 22.1).

Feeding behaviors

Variations occur among infants regarding interest in food, signs of hunger, and amount ingested at one time. The amount the infant consumes at any feeding depends on gestational and chronologic age, weight, hunger level, and alertness. When put to breast, some infants feed immediately, whereas others require a longer learning period. Random hand-to-mouth movement and sucking of fingers are well developed at birth and intensify when the infant is hungry. Caregivers should be alert and responsive to these hunger cues.

Signs of gastrointestinal problems

The time, color, and character of the infant’s first stool should be noted. Failure to pass meconium can indicate bowel obstruction related to conditions such as an inborn error of metabolism (e.g., cystic fibrosis) or a congenital disorder (e.g., Hirschsprung disease or an imperforate anus). An active rectal “wink” reflex (contraction of the anal sphincter muscle in response to touch) is a sign of good sphincter tone. Passage of meconium from the vagina or urinary meatus is a sign of a possible fistulous tract from the rectum.

Fullness of the abdomen above the umbilicus can be caused by hepatomegaly, duodenal atresia, or distention. Abdominal distention at birth usually indicates a serious disorder such as a ruptured viscus (from abdominal wall defects) or tumors. Distention that occurs later can be the result of overfeeding or can be a sign of a GI disorder. A scaphoid (sunken) abdomen, with bowel sounds heard in the chest and signs of respiratory distress, indicates a diaphragmatic hernia. Fullness below the umbilicus can indicate a distended bladder.

Some infants are intolerant of certain commercial infant formulas. If an infant is allergic or unable to digest a formula, the stools can become very soft with a high water content that is signaled by a distinct water ring around the stool on the diaper. Forceful ejection of stool and a water ring around the stool are signs of diarrhea. Care must be taken to avoid misinterpreting transitional stools for diarrhea. The loss of fluid in diarrhea can rapidly lead to fluid and electrolyte imbalance.

The amount and frequency of regurgitation, “spitting,” or vomiting after feedings should be documented. Color change, gagging, and projectile (very forceful) vomiting occur in association with esophageal and tracheoesophageal anomalies. Vomiting in large amounts, especially if it is projectile, can be a sign of pyloric stenosis. Bilious (green) emesis is suggestive of intestinal obstruction or malrotation of the bowel.

Iron storage

The fetal liver, which serves as the site for production of hemoglobin after birth, begins storing iron in utero. The infant’s iron store is proportional to total body hemoglobin content and length of gestation. At birth, the term infant has an iron store sufficient to last approximately 4 months. Iron stores of preterm and small-for-gestational-age infants are often lower and are depleted sooner than in healthy term infants. Although both breast milk and cow’s milk contain iron, the bioavailability of iron in breast milk (lactoferrin) is far superior.

Glucose homeostasis

The liver is responsible for regulation of blood glucose levels. In utero, the glucose concentration in the umbilical vein is approximately 80% of the maternal level. At birth, the newborn is removed from the maternal glucose supply, resulting in an initial drop in blood glucose from fetal levels of 70 to 90 mg/dL to levels of 55 to 60 mg/dL between 30 and 90 minutes after birth. During this time, glucagon levels increase while insulin levels decrease and the limited hepatic glycogen stores are mobilized. The initiation of feedings helps to stabilize blood glucose levels as milk lactose is metabolized. Glucose production also occurs through glycogenolysis and gluconeogenesis. Glucose levels rise gradually and stabilize by the second or third day at levels greater than 60 mg/dL (Garg & Devaskar, 2020).

Glucose levels are not routinely assessed in newborns unless there are risk factors or symptoms of hypoglycemia. Risk factors include small or large for gestational age, preterm, and infant of a diabetic mother. The hypoglycemic infant can be asymptomatic or can display the classic symptoms of jitteriness, lethargy, apnea, feeding problems, or seizures. Hypoglycemia in the initial newborn period is most often transient and easily corrected through feeding. Persistent or recurrent hypoglycemia necessitates intravenous glucose therapy and possible pharmacologic intervention.

Fatty acid metabolism

Fatty acid metabolism is an additional source of energy for the neonate in the initial hours after birth. Catecholamine release increases the rate of lipolysis, which produces fatty acids for oxidation and ketone body synthesis. Hepatic ketogenesis is increased in term newborns for the first 3 days.

Bilirubin synthesis

The liver is responsible for the conjugation of bilirubin, which results from the breakdown of RBCs. When RBCs reach the end of their life span, their membranes rupture, and hemoglobin is released. The hemoglobin is phagocytosed by macrophages; it then splits into heme and globin. The heme is broken down by the reticuloendothelial cells, converted to bilirubin, and released in an unconjugated form. The unconjugated (indirect) bilirubin is relatively insoluble and almost entirely bound to circulating albumin, a plasma protein. Bilirubin that is not bound to albumin, or free bilirubin, can easily cross the blood-brain barrier and cause neurotoxicity (acute bilirubin encephalopathy or kernicterus [see later discussion]).

The unconjugated bilirubin must be conjugated so it becomes soluble and excretable. In the liver, the unbound bilirubin is conjugated with glucuronic acid in the presence of the enzyme glucuronyl transferase. The conjugated form of bilirubin (direct bilirubin) is soluble and excreted from liver cells as a constituent of bile. Along with other components of bile, direct bilirubin is excreted into the biliary tract system that carries the bile into the duodenum. Bilirubin is converted to urobilinogen and stercobilinogen within the duodenum through the action of the bacterial flora. Urobilinogen is excreted in urine and feces; stercobilinogen is excreted in the feces (Fig. 22.6). The effectiveness of bilirubin excretion through the feces depends on the stooling pattern of the newborn and the substances in the intestine that break down conjugated bilirubin. In the newborn intestine, the enzyme β-glucuronidase is able to convert conjugated bilirubin into the unconjugated form, which is subsequently reabsorbed by the intestinal mucosa and transported to the liver; this is called enterohepatic circulation. Feeding is important in reducing serum bilirubin levels because it stimulates peristalsis and produces more rapid passage of meconium, thus diminishing the amount of reabsorption of unconjugated bilirubin. Feeding also introduces bacteria to aid in the reduction of bilirubin to urobilinogen. Colostrum, a natural laxative, facilitates the passage of meconium in breastfed infants.

When levels of unconjugated bilirubin exceed the ability of the liver to conjugate it, plasma levels of bilirubin increase and jaundice appears. Jaundice, the visible yellowish color of the skin and sclera, is likely to appear when the total serum bilirubin (TSB) level exceeds 6 to 7 mg/dL. Jaundice is generally noticeable first in the head, especially in the sclera and mucous membranes, and progresses gradually to the thorax, abdomen, and extremities. The degree of jaundice is determined by serum total bilirubin measurements (Kamath-Rayne, Froese, & Thilo, 2021).

The newborn is at risk for hyperbilirubinemia because of distinctive aspects of normal neonatal physiology. The higher RBC mass at birth and shorter life span of neonatal RBCs create the need for greater bilirubin synthesis. The ability of the liver to conjugate bilirubin is reduced during the first few days after birth; it can metabolize and excrete only approximately two-thirds of the circulating bilirubin. In addition, there are fewer bilirubin binding sites because newborns have lower serum albumin levels. In the intestines, conjugated bilirubin becomes unconjugated and recirculated through the enterohepatic circulation, which increases serum bilirubin levels.

Traditionally, newborn jaundice has been categorized as either physiologic or pathologic (nonphysiologic), depending primarily on the time it appears and on serum bilirubin levels. Controversy surrounds the definitions of normal or physiologic ranges of TSB. TSB levels in newborns are affected by variables such as gestational age, chronologic age, weight, race, nutritional status, mode of feeding, and presence of extravasated blood (e.g., cephalhematoma or severe bruising) (Blackburn, 2018). The time of onset of jaundice is a key factor in evaluating its cause and determining if treatment is needed.

Among the factors that increase the risk for hyperbilirubinemia, preterm birth is the most significant. Prematurity affects liver and brain metabolism and albumin binding sites, placing preterm and late preterm infants at greater risk for hyperbilirubinemia. Infants of Asian, Native-American, and Inuit ethnicity have higher bilirubin levels. Breastfeeding infants are at greater risk for hyperbilirubinemia (see later discussion) (Watchko, 2018). Risk factors for severe hyperbilirubinemia are listed in Box 22.2.

Coagulation

The liver plays an important role in blood coagulation. Coagulation factors, which are synthesized in the liver, are activated by vitamin K. The lack of intestinal bacteria needed to synthesize vitamin K results in transient blood coagulation deficiency between the second and fifth days of life. The levels of coagulation factors slowly increase to reach adult levels by 9 months of age. The administration of intramuscular vitamin K shortly after birth helps to prevent vitamin K deficiency bleeding (VKDB), which can occur suddenly and can be catastrophic (Letterio et al., 2020). Any bleeding problems noted in the newborn should be reported immediately and tests for clotting ordered.

Drug metabolism

The immaturity of the liver and depressed liver enzyme systems at birth result in slower biotransformation and elimination of drugs. This can result in slower drug clearance, increased serum levels, and longer half-lives (Blackburn, 2018).

Signs of hepatic system problems

Hypoglycemia and hyperbilirubinemia are the most common liver-related problems experienced by newborns. In most cases the problems are transient and require little if any treatment. Preterm infants are at increased risk for hepatic system problems because of the immaturity of the liver.

The hematologic status of all newborns should be assessed for anemia. For the first week of life, neonates are at risk for bleeding until the coagulation factors are well established. Male newborns who are circumcised prior to discharge from the birth facility must be monitored carefully for bleeding.

Risk for infection

All newborns, and preterm newborns especially, are at high risk for infection during the first several months of life. During this period, infection is one of the leading causes of morbidity and mortality. The newborn cannot limit the invading pathogen to the portal of entry because of the generalized hypofunctioning of the inflammatory and immune mechanisms.

Early signs of infection must be recognized so prompt diagnosis and treatment can occur. Temperature instability or hypothermia can be symptomatic of serious infection; newborns do not typically exhibit fever, although hyperthermia can occur (temperature greater than 38°C [100.4°F]). Lethargy, irritability, poor feeding, vomiting or diarrhea, decreased reflexes, and pale or mottled skin color are some of the clinical signs that suggest infection. Respiratory symptoms such as apnea, tachypnea, grunting, or retracting can be associated with infection such as pneumonia. Any unusual discharge from the infant’s eyes, nose, mouth, or other orifice must be investigated. If a rash appears, it must be evaluated closely; many normal rashes in the newborn are not associated with any infection. Infants must be protected from infections by the use of proper hand hygiene (see Chapter 35).

The greatest risk factor for neonatal infection is prematurity, because of immaturity of the immune system. Other risk factors include prelabor rupture of membranes, chorioamnionitis, maternal fever, antenatal or intrapartal asphyxia, invasive procedures, stress, and congenital anomalies.

Sweat glands

Distended, small, white sebaceous glands noticeable on the newborn face are known as milia (Fig. 22.7). Although sweat glands are present at birth, term infants usually do not sweat for the first 24 hours. By day 3, sweating begins on the face, then progresses to the palms. Infants can sweat as a function of body or environmental temperature; there can also be emotional sweating from crying or pain (Narendran, 2020).

Desquamation

Desquamation (peeling) of the skin of the term infant does not occur until a few days after birth. Large, generalized areas of skin desquamation present at birth can be an indication of postmaturity.

Congenital dermal melanocytosis

Congenital dermal melanocytosis or slate gray nevi (formerly known as Mongolian spots) bluish black areas of pigmentation, can appear over any part of the exterior surface of the body, including the extremities. They are most common on the back and buttocks (Fig. 22.8). These pigmented areas occur most frequently in newborns whose ethnic origins are Latin America, Asia, Africa, or the Mediterranean area, but can occur in White infants. (Blackburn, 2018). Slate gray nevi fade gradually over months or years.

The presence of slate gray nevi on the newborn should be documented carefully in the medical record. These normal skin pigmentations can be mistaken for bruises once the infant is discharged, and this can raise suspicion of physical abuse.

Nevi

Nevus simplex, also known as salmon patches, telangiectatic nevi, “stork bites,” or “angel kisses,” is the result of a superficial capillary defect and occurs in up to 80% of newborns. They are usually small, flat, and pink and are easily blanched (Fig. 22.9). The most common sites are the upper eyelids, nose, upper lip, and nape of the neck. They have no clinical significance and require no treatment. Facial lesions usually fade between the first and second years of life, whereas neck lesions can be visible into adulthood (Narendran, 2020).

A port-wine stain, or nevus flammeus, is usually visible at birth and is due to an asymmetric postcapillary venule malformation. It is usually pink and flat at birth but darkens with time, becoming red or purple and pebbly in consistency. True port-wine stains do not blanch on pressure or disappear. They are found most commonly on the face and neck (Narendran, 2020).

Infantile hemangioma

Infantile hemangiomas are the most common type of soft tissue tumors occurring in infants. They consist of dilated newly formed capillaries occupying the entire dermal and subdermal layers with associated connective tissue hypertrophy. The typical lesion is a superficial, raised, sharply demarcated, bright or dark red rough-surfaced swelling that may be present at birth or may appear during the early weeks after birth. Common sites are the scalp, face, back, and anterior chest. Some hemangiomas lie deeper in the skin as soft masses with bluish skin discoloration. Most superficial lesions reach maximum growth in approximately 6 months and then begin a slow process of involution. Deeper hemangiomas often continue to grow for a year or more (Narendran, 2020).

Erythema toxicum

Erythema toxicum, a transient rash, is also called erythema neonatorum, newborn rash, or flea bite dermatitis. It first appears in term neonates during the first 24 to 72 hours after birth and can last up to 3 weeks of age. It has lesions in different stages: erythematous macules, papules, and small vesicles (Fig. 22.10). The lesions can appear suddenly anywhere on the body. The rash is thought to be an inflammatory response. Eosinophils, which help to decrease inflammation, are found in the vesicles. Although the appearance is alarming, the rash has no clinical significance and requires no treatment (Narendran, 2020).

Signs of integumentary problems

Close observation of the newborn’s skin color can lead to early detection of potential problems. Any pallor, plethora (deep purplish color from increased circulating RBCs), petechiae, central cyanosis, or jaundice is noted and documented. The skin is examined for signs of birth injuries such as forceps marks and lesions related to fetal monitoring. Bruises or petechiae can be present on the head, neck, and face of an infant born with a nuchal cord (cord around the neck) or who had a face presentation at birth. Bruising can increase the risk for hyperbilirubinemia. Petechiae can be present if increased pressure was applied to an area. Petechiae scattered over the infant’s body should be reported to the health care provider because petechiae can indicate underlying problems such as low platelet count or infection.

Unilateral or bilateral periauricular papillomas (skin tags) occur fairly frequently. Their occurrence is usually a family trait and of no consequence.

Female

An increase in estrogen during pregnancy followed by a drop after birth causes female newborns to have mucoid vaginal discharge (Fig. 22.5) and even some slight bloody spotting. In term neonates, the labia majora and minora cover the vestibule (Fig. 22.11A). In preterm infants, the clitoris is prominent and the labia majora are small and widely separated. Vaginal or hymenal tags are common findings and have no clinical significance. Vernix caseosa can be present between the labia and should not be forcibly removed during bathing.

If the girl was born from a breech position, the labia can be edematous and bruised. The edema and bruising resolve in a few days; no treatment is necessary.

Male

In the uncircumcised newborn, the foreskin or prepuce completely covers the glans. The foreskin adheres to the glans and is not fully retractable for 3 to 4 years. The position of the urethra should be at the tip of the penis. With hypospadias, the urethral opening is located in an abnormal position, at any point on the ventral surface of the penis surface from the glans to the perineum. If the urethral opening is located on the dorsal surface of the penis, it is known as epispadias; this is less common and is often associated with exstrophy of the bladder (Elder, 2020). A common finding in newborn males are small, white, firm lesions called epithelial pearls at the tip of the prepuce.

By 28 to 36 weeks of gestation, the testes can be palpated in the inguinal canal and a few rugae appear on the scrotum. At 36 to 40 weeks of gestation, the testes are palpable in the upper scrotum and rugae appear on the anterior portion. After 40 weeks, the testes can be palpated in the scrotum and rugae cover the scrotal sac. The postterm neonate has deep rugae and a pendulous scrotum. Undescended testes (cryptorchidism) occur in approximately 4% of term newborn males and in 21% of preterm males; in most cases the testes gradually descend without intervention. Risk factors for cryptorchidism include preterm birth, low birth weight, maternal obesity, and cesarean birth (Sorbara & Wherrett, 2020).

The scrotum is usually more deeply pigmented than the rest of the skin (see Fig. 22.11B), particularly in darker-skinned infants. A bluish discoloration of the scrotum suggests testicular torsion, which needs immediate attention. If the male infant is born in a breech presentation, the scrotum can be very edematous and bruised (Fig. 22.12). The swelling and discoloration subside within a few days.

Hydrocele, caused by an accumulation of fluid around the testes, can be present. Hydroceles can be easily transilluminated with a light and usually resolve without treatment (Fig. 22.13).

Swelling of breast tissue

Swelling of the breast tissue in term infants of both sexes is caused by the hyperestrogenism of pregnancy. In a few infants a thin discharge (“witch’s milk”) can be seen. This finding has no clinical significance, requires no treatment, and subsides within a few days as the maternal hormones are eliminated from the infant’s body.

The nipples should be symmetric on the chest. Breast tissue and areola size increase with gestation. The areola appears slightly elevated at 34 weeks of gestation. By 36 weeks, a breast bud of 1 to 2 mm is palpable; this increases to 12 mm by 42 weeks.

Signs of reproductive system problems

The infant is inspected closely for ambiguous genitalia and other abnormalities. Normally in a female infant the urethral opening is located behind the clitoris. Any deviation from this can incorrectly suggest that the clitoris is a small penis, which can occur in conditions such as adrenal hyperplasia. Nearly all female infants are born with hymenal tags; absence of such tags can indicate vaginal agenesis. Fecal discharge from the vagina indicates a rectovaginal fistula. Any of these findings must be reported to the neonatal or pediatric health care provider for further evaluation.

Hypospadias, undescended testes, or other abnormalities of the male genitalia must be reported. Circumcision is contraindicated in the presence of hypospadias because the foreskin is used in repair of this anomaly.

Inguinal hernias can be present and become more obvious when the infant cries. They are common, especially in Black neonates, and usually require no treatment because they resolve with time.

Head and skull

Because of cephalocaudal (head-to-rump) development, the newborn looks somewhat out of proportion. The head at term is approximately one-fourth of the total body length. The arms are slightly longer than the legs. In the newborn, the legs are approximately one-third of the total body length. As growth proceeds, the midpoint in head-to-toe measurements gradually descends from the level of the umbilicus at birth to the level of the symphysis pubis at maturity.

The face appears small in relation to the skull. The skull appears large and heavy. Cranial size and shape can be distorted by molding (the shaping of the fetal head by overlapping of the cranial bones to facilitate movement through the birth canal during labor) (Fig. 22.14).

Caput succedaneum is a generalized, easily identifiable edematous area of the scalp, most often on the occiput (Fig. 22.15A). With vertex presentation, the sustained pressure of the presenting part against the cervix results in compression of local vessels, slowing venous return. The slower venous return causes an increase in tissue fluids within the skin of the scalp, and edema develops. This edematous area, present at birth, extends across suture lines of the skull and usually disappears spontaneously within 3 to 4 days. Infants who are born with the assistance of vacuum extraction usually have a caput in the area where the cup was applied. Bruising of the scalp is often seen in the presence of caput succedaneum.

Cephalhematoma is a collection of blood between a skull bone and its periosteum; it does not cross a cranial suture line (see Fig. 22.15B). A cephalhematoma is firmer and better defined than a caput. Often caput succedaneum and cephalhematoma occur simultaneously. A cephalhematoma usually resolves in 2 to 8 weeks. As the hematoma resolves, hemolysis of RBCs occurs, and hyperbilirubinemia can result.

Subgaleal hemorrhage is bleeding into the subgaleal compartment (see Fig. 22.15C). The subgaleal compartment is a potential space that contains loosely arranged connective tissue; it is located beneath the galea aponeurosis, the tendinous sheath that connects the frontal and occipital muscles and forms the inner surface of the scalp. Subgaleal hemorrhage is the result of traction or application of shearing forces to the scalp, commonly associated with difficult operative vaginal birth, especially vacuum extraction. The scalp is pulled away from the bony calvarium; the vessels are torn, and blood collects in the subgaleal space. Blood loss can be severe, resulting in hypovolemic shock, disseminated intravascular coagulation (DIC), and death (Prazad, Rajpal, Mangurten, et al., 2020).

Early detection of the hemorrhage is vital; serial head circumference measurements and inspection of the back of the neck for increasing edema and a firm mass are essential. A boggy scalp, pallor, tachycardia, and increasing head circumference can be early signs of a subgaleal hemorrhage. Computed tomography or magnetic resonance imaging is useful in confirming the diagnosis. Replacement of lost blood and clotting factors is required in acute cases of hemorrhage. Another possible early sign of subgaleal hemorrhage is a forward and lateral positioning of the newborn’s ears because the hematoma extends posteriorly. Monitoring the infant for changes in level of consciousness and decreases in hematocrit is also key to early recognition and management. An increase in serum bilirubin level may be seen as a result of the degradation of blood cells within the hematoma (Prazad et al., 2020).

Spine

The bones in the vertebral column of the newborn form two primary curvatures—one in the thoracic region and one in the sacral region. Both are forward, concave curvatures. As the infant gains head control at approximately 3 months of age, a secondary curvature appears in the cervical region. The newborn’s spine appears straight and can be flexed easily. The newborn can lift the head and turn it from side to side when prone. The vertebrae should appear straight and flat. If a pilonidal dimple is noted, further inspection is required to determine whether a sinus is present. A pilonidal dimple, especially with a sinus and nevus pilosis (hairy nevus), can be associated with spina bifida.

Extremities

The infant’s extremities should be symmetric and of equal length. Fingers and toes should be equal in number (five fingers on each hand and five toes on each foot) and should have nails present. Digits may be missing (oligodactyly). Extra digits (polydactyly) are sometimes found on the hands or feet. Fingers or toes may be fused (syndactyly).

The infant is examined for developmental dysplasia of the hips (DDH). In newborns with DDH, the affected hip is unlikely to be dislocated at birth; instead it is easily dislocatable after birth. Postnatal factors determine whether the hip dislocates, subluxates, or remains stable. DDH occurs more often in breech presentations (Fig. 22.16), first-born infants, female infants, and in infants with a family history of DDH (Son-Hing & Thompson, 2020; White, Bouchard, & Goldberg, 2018).

Signs of DDH are asymmetric gluteal and thigh skinfolds, uneven knee levels, a positive Ortolani test, and a positive Barlow test. The hips are inspected for symmetry. Gluteal and thigh skinfolds should be equal and symmetric, and legs should be of equal length (Fig. 22.17A). The level of the knees in flexion should be equal (see Fig. 22.17C). Hip integrity is assessed by using the Barlow test and the Ortolani maneuver. For the Barlow test, the examiner places the middle finger over the greater trochanter and the thumb along the midthigh. The hip is flexed to 90 degrees and adducted, followed by gentle downward pushing of the femoral head. If the hip can be dislocated with this maneuver, the femoral head moves out of the acetabulum, and the examiner feels a “clunk.” The hip is then checked to determine if the femoral head can be returned into the acetabulum using the Ortolani maneuver. As the hip is abducted and upward leverage is applied, a dislocated hip returns to the acetabulum with a clunk that is felt by the examiner (see Fig. 22.17B and D).

Signs of skeletal problems

Abnormalities of the skeletal system can be congenital, developmental, drug induced, or the result of intrapartum or postnatal factors. Signs of DDH, additional digits or webbing of digits, and any other abnormality should be documented and reported to the neonatal or pediatric health care provider.

A fractured clavicle often occurs in large infants and in those who had a difficult birth (e.g., shoulder dystocia). Unequal movement of the upper extremities or crepitus over the clavicular area can indicate fracture.

The newborn’s feet can appear to be abnormally positioned. This can indicate congenital deformity or can be related to fetal positioning in utero. For example, clubfoot (talipes equinovarus), a deformity in which the foot turns inward and is fixed in a plantar-flexion position, is a congenital condition that warrants attention. If the foot is turned inward in the plantar-flexion position but can be moved into the normal position, it is likely caused by fetal positioning and should gradually resolve.

Newborn reflexes

The newborn has many primitive reflexes. The times at which these reflexes appear and disappear reflect the maturity and intactness of the developing nervous system. The most common reflexes found in the normal term newborn are described in Table 22.1.

TABLE 22.1

Assessment of Newborn Reflexes

Reflex	Eliciting the Reflex	Characteristic Response	Comments
Rooting and sucking	Touch infant’s lip, cheek, or corner of mouth with nipple or finger.	Infant turns head toward stimulus and opens mouth in search of sucking source (e.g., nipple, finger); begins to suck when nipple or examiner’s finger is inserted into mouth.	Response is difficult if not impossible to elicit after infant has been fed; if response is weak or absent, consider preterm birth or neurologic defect. Parental guidance: Avoid trying to turn head toward breast or nipple; allow infant to root; response usually disappears after 3–4a months but can persist up to 1 year.
Swallowing	Feed infant; swallowing usually follows sucking and obtaining fluids.	Swallowing is usually coordinated with sucking and breathing and usually occurs without gagging, coughing, apnea, or vomiting.	If response is weak or absent, it can indicate preterm birth, effects of maternal analgesics or anesthetics, or illness that needs investigation. Sucking, swallowing, and breathing are often uncoordinated in preterm infant.
Grasp
Palmar	Place finger in palm of hand.	Infant’s fingers curl around examiner’s finger.	Palmar response lessens by 3–4 months; parents enjoy this contact with infant.
Plantar	Place finger at base of toes.	Toes curl downward around examiner’s finger.	Plantar response lessens by 8 months.
Extrusion	Touch or depress tip of tongue.	Newborn forces tongue outward.	Response disappears by about 4–5 months.
Glabellar (Myerson)	Tap over forehead, bridge of nose, or maxilla of newborn whose eyes are open.	Newborn blinks for first four or five taps.	Continued blinking with repeated taps is consistent with extrapyramidal signs.
Tonic neck or “fencing”	With infant in supine neutral position, turn head quickly to one side.	With infant facing left side, arm and leg on that side extend; opposite arm and leg flex (turn head to right, and extremities assume opposite postures).	Responses in leg are more consistent. Complete response disappears by 3–4 months; incomplete response may be seen until 3–4 years. After 6 weeks, persistent response is sign of possible cerebral palsy.
Moro	Hold infant in semisitting position, allow head and trunk to fall backward to angle of at least 30 degrees (with support). OR Place infant supine on flat surface; perform sharp hand clap.	Symmetric abduction and extension of arms are seen; fingers fan out and form a C with thumb and forefinger; slight tremor may be noted; arms are adducted in embracing motion and return to relaxed flexion and movement. A cry may accompany or follow motor movement. Legs may follow similar pattern of response. Preterm infant does not complete “embrace”; instead arms fall backward because of weakness.	Response is present at birth; complete response may be seen until 8 weeks; body jerk is seen only between 8 and 18 weeks; response is absent by 6 months if neurologic maturation is not delayed; response may be incomplete if infant is in deep sleep state; give parental guidance about normal response. Asymmetric response can indicate injury to brachial plexus, clavicle, or humerus. Persistent response after 6 months indicates possible neurologic abnormality.
Stepping or “walking”	Hold infant vertically under arms or on trunk, allowing one foot to touch table surface.	Infant will simulate walking, alternating flexion and extension of feet; term infants walk on soles of their feet, and preterm infants walk on their toes.	Response is normally present for 3–4 weeks.
Crawling	Place newborn on abdomen.	Newborn makes crawling movements with arms and legs.	Response should disappear by about 6 weeks of age.
Deep tendon	Use finger instead of percussion hammer to elicit patellar, or knee-jerk, reflex; newborn must be relaxed.	Reflex jerk is present; even with newborn relaxed, nonselective overall reaction may occur.	It is usually more difficult to elicit upper extremity reflexes than lower extremity reflexes.
Crossed extension	With infant in supine position, examiner extends one leg of infant and presses down knee. Stimulation of sole of foot of fixated limb should cause free leg to flex, adduct, and extend as if attempting to push away stimulating agent.	Opposite leg flexes, adducts, and then extends.	This reflex should be present during newborn period.
Babinski (plantar)	On sole of foot, beginning at heel, stroke upward along lateral aspect of sole; then move finger across ball of foot.	All toes hyperextend, with dorsiflexion of big toe—recorded as a positive sign.	Absence requires neurologic evaluation; should disappear after 1 year of age. Response depends on infant’s general muscle tone, maturity, and condition.
Pull-to-sit (traction response); postural tone	Pull infant up by wrists from supine position with head in midline.	Head lags until infant is in upright position; then head is held in same plane with chest and shoulder momentarily before falling forward; infant attempts to right head.	Response depends on general muscle tone and maturity and condition of infant.
Truncal incurvation (Galant)	Place infant prone on flat surface; run finger down back approximately 4–5 cm lateral to spine, first on one side and then down the other.	Trunk is flexed, and pelvis is swung toward stimulated side.	Response disappears by 4 weeks. Response varies but should be exhibited in all infants, including preterm. Absence suggests general depression of nervous system. With transverse lesions of cord, no response below level of lesion is present.
Magnet	Place infant in supine position, partially flex both lower extremities, and apply light pressure with fingers to soles of feet (Fig. A). Normally, while examiner’s fingers maintain contact with soles of feet, lower limbs extend.	Both lower limbs should extend against examiner’s pressure (Fig. B).	Absence suggests damage to central nervous system. Weak reflex may be seen after breech presentation without extended legs or may indicate sciatic nerve stretch syndrome. Breech presentation with extended legs may evoke exaggerated response.
Additional newborn responses: yawn, stretch, burp, hiccup, sneeze	These are spontaneous behaviors.	Responses can be slightly depressed temporarily because of maternal analgesia or anesthesia, fetal hypoxia, or infection.	Parental guidance: Most of these behaviors are pleasurable to parents. Parents need to be assured that behaviors are normal. Sneeze is usually a response to mucus in the nose and not an indicator of upper respiratory infection. No treatment is needed for hiccups; sucking may help. In a preterm infant, these are signs of neurodevelopmental immaturity and physiologic stress.

^aAll durations for persistence of reflexes are based on time elapsed after 40 weeks of gestation (i.e., if newborn was born at 36 weeks of gestation, add 1 month to all time limits given).

Gestational age

Gestational age and level of central nervous system (CNS) maturity affect infant behavior. In the preterm neonate with an immature CNS, the entire body responds to a pinprick of the foot, although the response may not be observed by an untrained observer. The more mature infant withdraws only the foot. CNS immaturity is reflected in reflex development, sleep-wake states, and ability (or lack thereof) to regulate or modulate a smooth transition between different states. Preterm infants have brief periods of alertness but have difficulty maintaining alertness without becoming overstimulated, which leads to autonomic instability unless intervention is implemented. Premature or sick infants show signs of fatigue or physiologic stress sooner than full-term healthy infants.

Time

The time elapsed since birth affects the behavior of infants as they attempt to become organized initially. Time elapsed since the previous feeding and time of day also can influence infants’ responses.

Stimuli

Environmental events and stimuli affect the infant’s behavioral responses. The newborn responds to animate and inanimate stimuli. Nurses in intensive care nurseries observe that infants respond to loud noises, bright lights, monitor alarms, and tension in the unit. If a mother is tense, nervous, or uncomfortable while feeding her infant, the infant may sense her tension and demonstrate difficulty feeding.

Maternal medication

No conclusive evidence exists regarding the effects of maternal analgesia or anesthesia during labor on neonatal behavior. Researchers who have studied the effects of epidural medications on breastfeeding behaviors have been unable to show a cause-and-effect relationship. In the postpartum period, there is concern about the effects of maternal opioid use on breastfeeding infants; transfer of opioids through breast milk can cause central nervous system depression in the infant resulting in sedation and respiratory depression (American College of Obstetricians and Gynecologists, 2018; Martin, Vickers, Landau, et al., 2018). Any medication taken by the breastfeeding mother has the potential for transfer to the infant through breastmilk. A resource on the safety of medications in breastfeeding mothers is LactMed: Drugs and Lactation Database, available from the National Library of Medicine (https://www.ncbi.nlm.nih.gov/books/NBK501922/).

Vision

At birth the eye is structurally incomplete, and the muscles are immature. The process of accommodation is not present but improves over the first 3 months of life. The pupils react to light, the blink reflex is stimulated easily, and the corneal reflex is activated by light touch. Term newborns can see objects as far away as 50 cm (2.5 feet). The clearest visual distance is 17 to 20 cm (8 to 12 inches), which is approximately the distance between the mother’s and infant’s faces during breastfeeding or cuddling. Newborns seem to have a preference for faces and can recognize the mother’s face. This facilitates interaction and promotes bonding. They will engage the mother or caregiver with eye contact. Newborns can imitate facial expressions and motions such as protruding the tongue. Newborns prefer complex patterns over nonpatterned stimuli. They prefer black and white, possibly because of the greater contrast. By 2 to 3 months, color discrimination occurs (Gardner & Goldson, 2021).

Hearing

Term newborns can hear and differentiate among various sounds. They will turn toward a sound and attempt to locate the source. The neonate recognizes and responds readily to the mother’s voice and shows a preference for high-pitched intonation. Newborns respond to rhythmic sounds. They are accustomed to hearing the regular rhythm of the mother’s heartbeat, which was a constant sound during intrauterine life. As a result, they respond by relaxing and ceasing to fuss and cry if a regular heartbeat simulator is placed nearby; a lullaby can have the same effect. Hearing is integral to bonding and attachment and may be more important than vision (Gardner & Goldson, 2021).

Routine hearing screening is recommended for all newborns before hospital discharge. See Chapter 23 for a discussion about newborn hearing screening.

Smell

Newborns have a highly developed sense of smell and can detect and discriminate distinct odors. It has been shown that preterm infants as early as 28 weeks are capable of reacting to odors. They react to strong odors such as alcohol or vinegar by turning their heads away but are attracted to sweet smells. By the fifth day of life, newborn infants can recognize their mother’s smell. Breastfed infants are able to smell breast milk and can differentiate their mothers from other lactating women.

Taste

Young infants are particularly oriented toward the use of their mouths, both for meeting their nutritional needs for rapid growth and for releasing tension through sucking. The early development of circumoral sensation, muscle activity, and taste would seem to be preparation for survival in the extrauterine environment. The newborn can distinguish among tastes and has a preference for sweet solutions (Gardner & Goldson, 2021).

Touch

The infant is responsive to touch on all parts of the body. The face (especially the mouth), hands, and soles of the feet seem to be the most sensitive. Reflexes can be elicited by stroking the infant. The newborn’s responses to touch suggest that this sensory system is well prepared to receive and process tactile messages (Gardner & Goldson, 2021). Early skin-to-skin contact with the mother promotes tactile interaction and stimulation. Touch and motion are essential to normal growth and development. However, each infant is unique, and variations can be seen in newborns’ responses to touch. Birth trauma or stress and depressant drugs taken by the mother can decrease the infant’s sensitivity to touch or painful stimuli.

Temperament

Each neonate has a unique repertoire of behaviors that are influenced by various factors including temperament, sensory threshold, ability to habituate, and consolability. Temperament refers to individual variations in the reaction pattern of newborns. Newborns possess individual characteristics that affect selective responses to various stimuli present in the internal and external environments. Some infants appear to be quiet by nature and can remain still for extended periods. Their movements may be smooth and relaxed most of the time, and they have little difficulty settling down for feeding. Other infants are more active and seem to be in constant motion; they seem to be excited and interested in exploring the faces and sounds around them. These infants often need help to settle; containment (swaddling), physical contact, and boundaries surrounding the infant in the crib can facilitate a quiet alert state.

Habituation

Habituation is a protective mechanism that allows the infant to become accustomed to environmental stimuli. It is a psychologic and physiologic phenomenon in which the response to a constant or repetitive stimulus is decreased. In the term newborn, this can be demonstrated in several ways. Shining a bright light into a newborn’s eyes causes a startle or squinting the first two or three times. The third or fourth flash elicits a diminished response, and by the fifth or sixth flash the infant ceases to respond (Brazelton & Nugent, 2011). The same response pattern holds true for the sounds of a rattle or stroking the bottom of the foot.

The ability to habituate allows the healthy term newborn to select stimuli that promote continued learning about the social world, thus avoiding overload. The intrauterine environment seems to have programmed the newborn to be especially responsive to human voices, soft lights, soft sounds, and sweet tastes.

The newborn quickly learns the sounds in the home environment and is able to sleep in their midst. The selective responses of the newborn indicate cerebral organization capable of memory and making choices. The ability to habituate depends on the state of consciousness, hunger, fatigue, and temperament. These factors also affect consolability, cuddliness, irritability, and crying.

Consolability

Newborns vary in the ability to console themselves or be consoled. In the crying state, most newborns initiate one of several ways to reduce their distress. Hand-to-mouth movements with or without sucking and being alert to voices, noises, or visual stimuli are common. Some infants are consoled only if they are held and rocked (Brazelton & Nugent, 2011).

Cuddliness

Cuddliness is especially important to parents because they often gauge their ability to care for the child by the child’s responses to their actions. The degree to which newborns relax and mold into the contours of the person holding them varies. One extreme is the infant who always resists being held with thrashing and stiffening of the body. This is in contrast to the infant who immediately relaxes when held and molds to the body of the person. Less extreme behavior is demonstrated by infants who are passive when held and those who gradually mold after being held for a while (Brazelton & Nugent, 2011).

Irritability

Some newborns cry longer and harder than others. For some, the sensory threshold seems low. They are easily upset by unusual noises, hunger, wetness, or new experiences and thus respond intensely. Others with a high sensory threshold require a great deal more stimulation and variation to reach the active, alert state.

Crying

Crying is the language an infant uses most often to communicate needs. It can signal hunger, discomfort, pain, desire for attention, or fussiness. Infants may cry in response to environmental stimuli such as cold, being overstimulated, or being held by multiple persons. Responsiveness of the caregiver to the crying creates trust as the infant learns to associate the caregiver with comfort.

The amount and tone of crying vary based on gestational age, weight, and the reason for the cry (e.g., hunger, pain). A high-pitched cry can be a sign of a neurologic disorder. Some mothers state that they learn to distinguish among the cries. The breastfeeding mother’s body responds physiologically to infant crying by stimulating the milk-ejection reflex (“let-down”).

The duration of crying also varies greatly in each infant; newborns may cry for as little as 5 minutes or as much as 2 hours or more per day. The amount of crying peaks in the second month and then decreases. There is a diurnal rhythm of crying, with more crying occurring in the evening hours.