Prematurity continues to be an issue of major concern as the rate of preterm birth continues to rise. The significance of this change in birth demographics is the higher risk of morbidity and mortality among infants born early. In the United States alone, preterm birth accounts for over 500,000 infants born prematurely each year. Recent birth data from the National Center for Health Statistics Vital Statistics Report indicate that induction and cesarean delivery rates have increased, leading to a decline in the mean gestational age at delivery of 39 weeks (Figure 92-1). Postterm birth has also declined. Since 1990 the rate of preterm birth less than 37 weeks' gestation has risen dramatically from 10.6% to 12.7% in 2004. This increase in preterm birth has occurred among all racial and ethnic groups.[1] Shorter-than-normal gestation is the result, in part, of an increase in multiple births.[2] However, the increase in prematurity has occurred among singleton gestations as The National Vital Statistics Surveillance System continues to record an increasing rate of preterm birth for 2005 and 2006 among singleton and total pregnancies.

Figure 92-1 Percentage distribution births by gestational age (32-44 weeks): United States, 1990 and 2004. (Martin JA, Hamilton BE, Sutton PD, et al. Births: Final Data From 2004. National Vital Statistics Reports. Vol. 55, no. 1. Hyattsville, MD: National Center for Health Statistics; 2006. Available at: www.cdc.gov/nchs/products/pubs/pubd/hestats/prelimbirths05.htm.)

Prematurity encompasses a broad range of infants born between 23 and 36 weeks' gestation. Within this large group of neonates, preterm babies can be grouped in categories based on their degree of immaturity. Previous convention described infants born before 28 weeks' gestation as extremely premature, whereas infants born before 32 weeks were classified as very preterm and infants born between 35 and 37 weeks were labeled near term. Recognition of the increased vulnerability associated with birth between 34 and 36 weeks' gestation and the variability in the terminology used to describe infants at different gestational and postnatal ages led to the publication of the American Academy of Pediatrics (AAP) Committee on Fetus and Newborn “Policy Statement: Age Terminology During the Perinatal Period,”[3] which defines the terms commonly used to describe the length of gestation and the age of the infant (chronologic, postmenstrual, and corrected age) (Figure 92-2). The National Institute for Child Health and Human Development during a 2005 Workshop on Optimizing Care and Long-term Outcome of Near-Term Pregnancy and Near-Term Newborn Infants (Bethesda, MD, July 18-19, 2005) refined the definition of late preterm birth to mean delivery from 34 0/7 to 36 6/7 weeks' gestation (239 to 259 days).[4]

Figure 92-2 Age terminology during perinatal period.

Births between 34 and 36 weeks' gestation have increased more markedly than preterm births less than 34 weeks' gestation and now account for 71% of all premature births (Figure 92-3). In contrast, little change has occurred in the number of births between 32 and 33 weeks' gestation. Thirty-seven percent of preterm infants are born at 36 weeks' gestation. The distribution of preterm births among the remainder of babies born prematurely is 21% at 35 weeks' and 13% at 34 weeks' gestation (Figure 92-4 and Figure 92-5). As a group, late preterm infants experience greater mortality and morbidity than their full-term counterparts.[5] Deaths resulting from congenital malformations, immaturity, asphyxia, infection, and sudden infant death are 4 to 26 times higher among this group of babies than those born between 38 and 41 weeks' gestation. Late preterm infants represent 33% of total neonatal intensive care unit (NICU) admissions.[4] With increasing gestational maturity, the percentage of preterm infants requiring intensive care decreases. Estimates suggest that 50% of infants born at 34 weeks' gestation require NICU admission, in contrast to 15% of infants born at 35 weeks and 8% of babies at 36 weeks.[6] [7]

Late preterm infants are more likely to exhibit difficulty with thermoregulation and control of cardiorespiratory function (apnea, bradycardia, and hypoxic episodes); to develop problems with oral feeding, hypoglycemia, hyperbilirubinemia, and suspected sepsis; and to experience an increased incidence of respiratory distress resulting from immaturity.[6] Costs for prolonged hospitalization and associated medical care of late preterm infants are more than 40% higher for this group of infants. Infants born at 34 weeks' gestation often require resuscitation and neonatal intensive care. Irrespective of the presence of respiratory distress, the preterm infant between 34 and 36 weeks' gestation is prone to feeding difficulties and hyperbilirubinemia. Despite the increased risk of morbidity, many late preterm newborns are routinely cared for in regular newborn or well-baby nurseries after their birth rather than a special (level II) or neonatal intensive (level III) care unit and are frequently discharged home at 2 to 3 days of age. The higher birth weights of these infants, often within the normal birth weight range, over 2500 g, result in many late preterm infants being treated the same as their developmentally more mature full-term counterparts. The assumption that late preterm infants have similar risks as term infants is common. Transitional issues such as transient tachypnea of the newborn, cold stress, and hypoglycemia can be easily missed during the early hours after birth if particular attention is not paid these aspects of the transition.

The AAP-American College of Obstetrics and Gynecology[8] and the AAP Committee of Fetus and Newborn[9] specify that infants younger than 35 weeks' gestation should be cared for in a speciality nursery or NICU (level II or III neonatal unit). However, the variation in the actual scope of care within neonatal units presents a challenge to identifying best practices related to the optimal level of newborn care for the late preterm infant. Individual hospital policies and, in institutions in which regionalized perinatal health systems are in place, neonatal transfer policies currently guide when care for subsets of babies within this group occurs. The criteria determining whether an apparently healthy preterm may be cared for in a regular newborn nursery are based on the gestational age, birth weight, need for resuscitation, and transitional care.

The late preterm infant is also at increased risk for ongoing health and developmental problems. Approximately 7%-9% of newborns 34 to 36 weeks' gestation require rehospitalization within 14 days of nursery discharge.[7] The most common cause for readmission is hyperbilirubinemia. An important point to note is that late preterm newborns, particularly those between 35 to 36 weeks' gestation, are at risk for kernicterus as a complication of unrecognized and untreated hyperbilirubinemia. Less frequent, but still important, reasons for rehospitalization include dehydration and feeding difficulties, suspected sepsis, and prolonged or severe illness.[10] [11] Infants born between 35 and 36 weeks' gestation account for 58% of preterm births and are reported to be four times more likely to be readmitted than a term baby, particularly if the newborn's age at discharge was less than 72 hours.[7] [12]

Figure 92-3 Percentage distribution preterm births, United States, 2004.

Figure 92-4 Distribution of preterm births by gestational age, United States, 2003.

Figure 92-5 Percentage of preterm births: United States, 1990, 2004, and 2005. (Hamilton BE, Martin JA, Ventura SJ. Births: Preliminary Data for 2005. National Vital Statistics Reports. Vol 55. Hyattsville, MD: National Center for Health Statistics; 2006. Available at: www.cdc.gov/nchs/products/pubs/pubd/hestats/prelimbirths05.htm; www.cdc.gov/nchs/products/pubs/hestats/prelimbirths05.htm#ref01. Accessed May 15, 2007.)

Preterm newborns have an impaired ability to prevent heat loss and to increase their body heat production in response to low environmental temperatures. The risk of cold stress is greatest during the immediate transitional period after delivery and is caused by the preterm newborn's immature skin, the high ratio of surface area to birth weight, and the environmental conditions in the delivery room (large temperature gradients between the newborn's body temperature and the ambient temperature of delivery room, air flow through the room, and contact with cold surfaces that lead to significant evaporative, radiant, convective, and conductive heat losses). Wide variations in delivery room temperatures have been reported to have a significant effect on a newborn's temperature.[13] [14] Approximately 50% of newborns experience some degree of cold stress after birth.

Oxidation of fatty acids is the predominant method of nonshivering heat production in newborns regardless of gestational age or birth weight. Brown fat, the major store of fatty acids in neonates, is located around the mediastinal structures, kidneys, scapulae, axillae, and nape of the neck. Cold exposure activates the sympathetic nervous system, releasing norepinephrine. Norepinephrine, in turn, stimulates the hydrolysis or breakdown of brown fat, with resultant heat production. Late preterm newborns have less brown fat in comparison with term infants. Consequently, they are more prone to develop cold stress and hypothermia. Normal core body temperature for a neonate is 36.5° to 37.4° C (97.7° to 99.3° F). Clinical manifestations of cold stress are nonspecific and may be misinterpreted as signs of sepsis. Common findings include tachypnea, peripheral vasoconstriction, pallor, mottling caused by vasomotor instability, and metabolic acidosis. Therefore maintaining thermoneutrality, keeping the newborn warm and dry while minimizing heat loss, and energy expenditure are important components of the preterm newborn's initial care.

Strategies to minimize heat loss include the following:

• Maintain the delivery room and all other patient care rooms at a temperature of 24° ±2° C (75° ±3° F) or 22° to 26° C (72°-78° F), with a humidity of 30% in the winter and 50% in the summer.[15] [16]
• Rapidly dry the newborn after delivery.
• Cover the newborn's head with a hat to reduce heat loss.
• Initiate skin-to-skin contact with the mother to facilitate temperature regulation of the newborn.
• Place the newborn in an isolette when not skin-to-skin with the mother if the newborn is exhibiting difficulty maintaining the body temperature.

Acute respiratory distress is the most common condition experienced by the late preterm newborn.[10] [17] [18] [19] Neonates born between 34 and 36 weeks' gestation who exhibit respiratory distress after delivery are at increased risk for associated morbidities. These infants frequently require stabilization and treatments such as supplemental oxygen and assisted ventilation.[20] Late preterm newborns exhibit higher rates of low Apgar scores, transient tachypnea of the newborn (TTN), respiratory distress syndrome (RDS), persistent pulmonary hypertension, and respiratory failure. TTN and RDS are both common in the late preterm newborn and are related to delayed clearance of lung fluid, surfactant deficiency, or both. By one estimate, nearly one third of late preterm newborns will exhibit respiratory difficulties.[6] Late preterm male infants more often exhibit respiratory distress than late preterm girls. Neonates who are born by cesarean delivery before labor begins are at increased risk for respiratory distress. Labor initiates hormonal changes necessary for normal pulmonary transition and function. Hemodynamic instability caused by hypothermia or hypoglycemia may worsen the newborn's underlying respiratory distress.

Smooth respiratory transition is important to prevent respiratory distress. In utero, alveoli are filled with fluid that must clear during the initial transitional period for effective ventilation to be established. In addition, pulmonary blood flow to the lungs must increase to ensure effective pulmonary perfusion and adequate matching of perfusion and ventilation. A significant part of this process includes fluid clearance via transepithelial sodium absorption and through the mechanical squeeze and Starling forces that occur during the process of labor and vaginal delivery. Liquid is also driven through the pulmonary epithelium into the vasculature. Maturation and recruitment of epithelial sodium channels occur during the last few weeks of pregnancy in response to endogenous steroid and cathecholamine surges that are triggered by the onset of labor. Neonatal transition becomes difficult when the infant is born by cesarean delivery without spontaneous labor. Impaired function or inactivity of the sodium channel contributes to TTN and RDS. Although administering antenatal corticosteroids results in a significant reduction in mortality and morbidity caused by RDS in premature infants younger than 34 weeks' gestation, meta-analyses have not shown as dramatic benefit for infants older than 34 weeks' gestation, given that nearly 100 women presenting in preterm labor at this gestation would require treatment to prevent one case of RDS.[21] As a consequence, antenatal corticosteroids are not routinely used in the care of the woman in preterm labor or the woman who has a medical complication at 35 to 36 weeks' gestation that may necessitate early delivery.

Strategies to minimize the risk for respiratory morbidity include the following:

• Personnel skilled in the assessment, resuscitation, and stabilization of the preterm newborn should be present in the delivery room.
• Initial evaluation should include assessment of respiratory stability with consideration of early initiation of continuous positive airway pressure if respiratory distress is present; continuing respiratory care needs will be determined by the cause of the newborn's respiratory distress.
• Attention should be paid to maintaining thermoneutrality and glucose homeostasis to avoid additional morbidity that may prolong the newborn's physiological transition and respiratory signs.

The decision as to the site of care (regular newborn nursery versus a NICU) for the well-appearing late preterm newborn will depend on specific hospital policy and the newborn's gestational assessment. Many hospitals have policies that require the 34 weeks' gestational age newborn to be admitted to a transitional care nursery or a NICU; once the newborn completes the transitional period, shows no signs of respiratory or temperature instability, and demonstrates the ability to satisfactorily feed, the newborn may be transferred to a regular nursery to complete the required care.

Prematurity, hypothermia, hypoxia, maternal diabetes, maternal glucose infusion in labor, and intrauterine growth restriction are each factors that contribute to the incidence of hypoglycemia. Hypoglycemia occurs more frequently in late preterm newborns than in term newborns as a result of decreased hepatic glycogen stores and delayed hepatic glucose 6-phosphatase dehydrogenase activity in response to hypoglycemia.[22] [23] [24]

The preterm newborn also has decreased availability of amino acids for gluconeogenesis and inadequate lipid stores for release of fatty acids and fat stores to maintain glucose balance. Feeding is less efficient in some late preterm infants than in term newborns because of easy fatigability and immature feeding skills. Limited enteral intake further complicates the newborn's initial transition, predisposing the late preterm newborn to hypoglycemia. Hypoglycemia has been reported to occur four to five times more frequently in newborns born at 35 to 36 weeks' gestation in comparison with infants born at term.[6] An important element of care in prevention of hypoglycemia in the late preterm newborn is appropriate risk assessment with glucose screening of babies at risk. (See Chapter 104, Common Metabolic Disturbances in the Newborn.) The late preterm newborn should be able to maintain the blood glucose level above 2.6 mmoL/L (47 mg/dL).

Strategies to minimize the risk for hypoglycemia include the following:

• Initiate early feedings to maintain glucose balance.
• Monitor glucose. Blood glucose levels should be monitored on nursery admission and every 1 to 3 hours thereafter based on the specific risk factors for a period of at least 3 to 6 hours after birth.
• Optimize enteral intake. Newborns with oral feeding difficulty should be gavage (tube) fed until effective oral feeding is achieved.
• Breastfeeding:
  • Allow feeding on demand with close attention to the newborn's state regulation and ability to express hunger cues.
  • Provide lactation consultation within 24 hours of birth.
  • The mother should initiate milk expression within 4 to 6 hours after delivery if the newborn is not able to nurse effectively.
• Provide supplemental feedings by bottle or gavage if the oral enteral intake is inadequate and the newborn exhibits excessive weight loss of greater than 10% or more than 3% per day.
• Consider increasing caloric density by feeding 22- to 24-cal/oz or fortifying expressed breast milk for newborns with excessive weight loss or persistently poor weight gain.

Late preterm infants are susceptible to infection, either congenital or acquired, because of immaturity of their immune system. (See Chapter 101, The Infant With Suspected Infection.) As a group, late preterm infants are nearly four times more likely to be evaluated for suspected sepsis than the full-term neonate and are more likely to be treated with a 7-day course of antibiotics.[6] This is related to the frequent presence of preterm birth risk factors that suggest infection. In addition, clinical signs suggestive of early systemic infection are common during the transitional period. These signs include respiratory distress, temperature instability, low tone, poor feeding, and, in some cases, evidence of hemodynamic instability.

Strategies to minimize morbidity related to infection risks include the following:

• Carefully review the maternal medical history and intrapartum course, including the administration of intrapartum antibiotics, to identify specific risk factors for infection and any treatments used to moderate infectious risks.
• Carefully monitor and thoroughly assess the infant for signs of infection, and initiate therapy as appropriate. Some hospitals use algorithms or practice guidelines based on the Centers for Disease Control and Prevention (CDC) Group B Streptococcal Disease Revised Guidelines.[25]
• Encourage early and exclusive breastfeeding, either by direct breastfeeding or the provision of expressed breast milk.

Maturation of the gastrointestinal tract is important not only for digestion and absorption, but for endocrine and exocrine function as well. Increases in the intestinal length and surface area including villus and microvillus growth occur during the last trimester. The majority of late preterm newborns are able to tolerate human milk and formula without difficulty despite these developmental differences. Although the late preterm newborn has low gastric acid secretion and limited pancreatic enzyme activity, preterm newborns are able to digest whole protein formulas.[26] [27] Decreased bile acid secretion and enterohepatic circulation suggest that the late preterm infant might have difficulty digesting fats. However, a meta-analysis of studies comparing medium-chain triglyceride to long-chain triglyceride as the fat fed to preterm infants did not show a difference in weight gain.[28] Late preterm infants are able to digest carbohydrate despite lower lactase activity. Premature infants frequently have intestinal motor function immaturity that contributes to feeding intolerance. Intestinal dysmotility is typically present up to 34 weeks' gestation but may persist in some late preterm infants. Suck and swallow coordination is often poor before 34 weeks' gestation. Some infants may require a longer-than-normal interval between feedings because of a delay in motility and gastric emptying.

Human milk provides substantial benefits to premature infants' health. Human milk intake is associated with reduced infectious and inflammatory disease, enhanced neurodevelopmental outcome, and maintains healthy postnatal growth patterns. An important point to consider is the adequacy of the infant's intake and growth on the chosen feeding. Many late preterm infants have poor state regulation and are not able to demonstrate clear feeding cues properly. In addition, the strength and efficiency of the suck patterns and suck-swallow-breathing coordination may further impede successful oral feeding and contribute to excessive weight loss or poor weight gain. Little research has been conducted on specific feeding regimens for the late preterm infant. Most feeding recommendations are geared toward the low–birth-weight infant. Low birth weight, defined as a birth weight below 2500 g (5.5 lb), can be subgrouped into babies with a birth weight between 1501 and 2000 g (3.3 and 4.4 lb) or infants with a birth weight between 2001 and 2500 g (4.4 and 5 lb). Primary care physicians must assess the adequacy of caloric and nutrient intake and offer parents guidance. Decisions to be considered include:

1. Whether the breastfeeding infant requires supplementation as a result of excessive weight loss or inadequate weight gain
2. When appropriate, which formula should be used: a full term formula or an enriched post discharge preterm formula
3. If the late preterm infant is also small-for-gestational age (<5%), whether birth weight or gestational age should determine what feeding to use
4. Whether any red flags exist that increase concern about adequacy of the infant's intake:
   1. Feeding duration greater than 30 minutes or fewer than six feedings per day after the first 24 hours of life
   2. Fussiness, distress, or difficulty breathing during feeding; difficulty waking the infant for feeding; difficulty completing a feeding
   3. Lethargy or decreased arousal during feeding
   4. Feed refusal, arches during feeding, gags, coughs, chokes frequently while feeding

Strategies to consider when determining the feeding regimen include the following:

• Human milk should be the first choice for infants between 34 and 36 weeks' gestation.
  • Infant should be breastfed 8 to 12 times per day.
  • Supplementation with a transitional formula may be considered for the infant with a birth weight between 1500 and 2000 g until the infant is able to sustain weight gain and breastfeed fully without difficulty.
• Use of human milk fortifier is typically limited to:
  • Infants younger than 34 weeks' gestation
  • Infants with a birth weight less than 1500 g to 1800 g
  • Infants who required greater than 2 weeks of parenteral nutritional support
  • Infants with specific nutritional risks caused by chronic medical conditions or complications of prematurity
• Provide early postnursery discharge follow-up care within 48 to 72 hours to assess feeding adequacy, hydration, and weight.
• Formula-fed infants with birth weight between 1500 and 2000 g should receive an enriched post discharge formula until 6 to 9 months corrected age. Calcium and phosphorus levels should be monitored.
• Growth parameters should be plotted on a Fenton growth curve[29] (revised Babson-Benda growth curve; Figure 92-6) or a 2000 CDC growth chart. (See Chapter 14, Pediatric Physical Examination.)
• Enriched formula feeding should be discontinued if:
  • Infant is not able to tolerate it.
  • Infant demonstrates excessive weight gain greater than 40 g/day or is above the 50th percentile on the CDC growth chart.
  • Calcium and phosphorus levels exceed normal ranges for age.
• Infants with birth weight greater than 2000 g should be breastfeeding on demand or if formula feeding receive a standard (term) 20 cal/oz iron fortified formula. If supplementation is required because of inadequate weight gain or excessive weight loss, then a standard formula may be considered.

Soy formulas are not recommended for preterm infants born at less than 1800 g.[30]

Figure 92-6 Babson-Benda growth curve.

Prematurity is the main risk factor for hyperbilirubinemia and is associated with an increased risk of kernicterus.[31] [32] Jaundice in the late preterm infant often has a more severe and protracted course than in term infants. Bilirubin levels typically peak between 5 and 7 days in the premature infant and decline slowly thereafter. Kernicterus is a preventable brain injury; failure to diagnose and treat properly the late preterm infant with significant hyperbilirubinemia may place the clinician at medical-legal risk. Table 92-1 summarizes recommended interventions for various bilirubin levels in late preterm infants. In late preterm infants the progression to kernicterus can be insidious. Late preterm newborns discharged home within 72 hours of birth should have a follow-up appointment within 2 to 3 days of their discharge (within the first week of life). (See Chapter 98, Neonatal Jaundice.)

Risk for BIND (AAP Guidelines*)	TSB Threshold at Age 48 hr (mg/dL)		TSB Threshold at Age ≥96 hr (mg/dL)
	Phototherapy	Exchange	Phototherapy	Exchange
High (presence of any BIND risk factors and 35-0/7 to 37-6/7 wk)	11	18	15	19
Moderate (35-0/7 to 37-6/7 wk with no BIND risk)	13	20	18	22.5
Low (term infant with no BIND risk)	15	22	21	25

AAP, American Academy of Pediatrics; BIND, bilirubin-induced neurologic dysfunction; TSB, total serum bilirubin.
BIND risk factors: isoimmune hemolytic anemia; glucose-6-phosphate dehydrogenase deficiency: significant lethargy, sepsis, acidosis, asphyxia, temperature instability, and serum albumin level <3.0 g/dL.
^*American Academy of Pediatrics. Subcommittee on Hyperbilirubinemia. Clinical practice guidelines. Management of hyperbilirubinemia in the newborn infant 35 or more weeks of gestation. Pediatrics. 2004;114(1):297-316.

The majority of the brain growth occurs during the last half of gestation, with 35% of the brain's weight accrued in the last 6 weeks of gestation.[33] Although neuronal proliferation and migration are considered complete by 24 weeks, the brain's gyri and sulci are not fully developed in the late preterm infant. In addition, a 4-fold (50%) increase in cortical brain volume occurs during the third trimester.[34] Synaptogenesis, dendritic branching, and maturation of oligodendrocytes also continue through the last weeks of gestation. These processes are extremely sensitive and susceptible to hypoxic-ischemic and free radical injury, particularly the oligodendrocytes. Cerebral palsy (CP) is the most common early neurodevelopmental impairment in infancy. Among children with CP, approximately one third will have been born between 32 and 36 weeks' gestation.[35] CP develops in response to two types of white matter injury involving (1) focal necrosis in the periventricular region (periventricular leukomalacia) and (2) diffuse injury to the surrounding central white matter, basal ganglia, and thalamus.[36] (See Chapter 245, Cerebral Palsy.)

Brainstem function and autonomic and respiratory control are also immature, contributing to periodic breathing, apnea, desaturations, and bradycardia in the preterm infant. As previously described, inefficient feeding skills in conjunction with poor coordination of suck-swallow-breathing and episodic gastroesophageal reflux precipitate these physiological responses. The incidence of sudden infant death syndrome in preterm infants between 33 and 36 weeks' gestation is 1.37/1000 live births compared with 0.69/1000 term infants.[5] For infants between 34 and 37 weeks' gestation the relative risk of experiencing an episode of prolonged apnea or bradycardia requiring intervention (apparent life-threatening event) is three times greater than the term infant. The Collaborative Home Infant Monitoring Evaluation (CHIME) study found that 30% of the study infants who experienced an apparent life-threatening event were less than 38 weeks' gestation at birth. The younger the preterm infant was, the earlier symptoms were exhibited.[37] (See also Chapter 237, Apparent Life-Threatening Events.)

Consequently, some hospital practices and primary care physicians may consider polysomnographic evaluation of the late preterm infant before nursery discharge or recommend home monitoring. However, no data are available that support the routine use of predischarge testing or home monitoring for this group of infants. Considerations regarding these care recommendations should be based on the infant's clinical and family history. Parents of late preterm infants should be counseled that their babies should be placed supine for sleep and that all other recommendations regarding safe sleep practices are applicable to their preterm infant. If the mother plans to practice bed sharing with her infant, then instructions should be provided on how to do so safely.

Gestational age-specific long-term outcome data about the late preterm infant are limited. Studies have primarily reported on outcomes of infants with varying degrees of low birth weight. Care must be taken when interpreting this information because included among infants in these studies are small-for-gestational-age infants, some of whom may have been term. Population-based studies have revealed that the risk of developmental delay or disability is 40% higher for infants weighing between 1500 and 2499 g at birth in comparison with normal–birth-weight babies.[38] Educational outcomes for children born premature are similarly affected. Although the greatest effect is among the most immature infants weighing less than 1000 g at birth, heavier low–birth-weight children experience increased adverse educational outcomes in the areas of academic problems, learning disabilities, physical and sensory impairments, and mental disabilities.[39] Investigators have reported school performance outcomes for children born after 32 weeks' gestation. Reading and spelling difficulties are more frequent among children born at 33 to 36 weeks' gestation than normal–birth-weight infants.[40] Huddy et al reported on school performance at age 7 years for a population-based cohort of children born between 32 and 35 weeks' gestation. Up to one third of these children exhibited school difficulties. Nearly 25% required additional school resources. Areas of identified poor performance included writing, fine motor skills, reading, mathematics, and physical education.[41] The risk of developing attention-deficit/hyperactivity disorder is nearly two and one-half times greater than for normal–birth-weight children.[42] Behavioral difficulties are twice as common in low–birth-weight children and have been shown to be related to maternal psychological distress at term (40 weeks) postmenstrual age and a history of tobacco exposure. Whether the effects of smoking are primary or a proxy for other environmental factors or stressors that influence parental well being and their ability to support their child's maturation is unclear.[43] Therefore the clinician should monitor the child's behavioral and educational progress because the late preterm infant is not typically considered automatically eligible for early intervention services and may not even be viewed as at-risk under early intervention guidelines from the Child Find initiative.

According to the CDC Advisory Committee on Immunization Practices recommendations, late preterm infants born to hepatitis B surface antigen–positive mothers should receive hepatitis B (HBV) vaccine and hepatitis B immune globulin (HBIg) within 12 hours of birth. In neonates whose birth weight is less than 2000 g, the initial vaccine dose confers lower immunogenicity than infants born at term. Therefore infants younger than 34 weeks' gestation or weighing less than 2000 g should receive a total of four doses of HBV vaccine (birth and 1-2, 3-4, and 6 months). In case of unknown maternal status at delivery, infants weighing less than 2000 g should receive both HBV vaccine and HBIg. Neonates born to hepatitis B surface antigen–negative mothers should receive the first dose of vaccine in the hospital.

According to Federal Motor Vehicle Safety policy the maximal weight acceptable for use of an infant car seat safety is 50 lb; however, no minimal weight is specified. Preterm infants have been shown to have episodes of oxygen desaturation when placed in a standard upright infant car seat. Infants transported in car beds are less likely to exhibit desaturations. Many hospitals routinely measure the adequacy of the infant's oxygenation while in the car seat before hospital discharge to assist parents with proper positioning of the baby and to reduce the risk for cardiorespiratory compromise. Rolled towels or blankets may be placed on both sides of infant for head and neck support. Infants who exhibit apnea, bradycardia, and desaturations while upright are advised to travel in a supine position in a car bed. Babies discharged with home monitoring should also be monitored during travel. For the infant discharged on oxygen, proper storage of the oxygen tank and apnea monitor during travel includes placing the equipment below the infant seat or on the vehicle floor for safety purposes.

All newborn screening procedures should be conducted. Newborn hearing screening using either automated auditory brainstem response or otoacoustic emission testing devices is feasible and should be completed before the late preterm infant is discharged from the newborn nursery. Follow-up care should include a home nurse visit or an office visit with the primary care physician within 48 to 72 hours of the newborn's discharge from the hospital. If the newborn is younger than 5 days at the time of nursery discharge, is breastfeeding, or has any risk factors for potential difficulties, then follow-up should occur within 48 hours of hospital discharge.

• Care Safety Seats: A Guide for Families, 2007 (brochure), American Academy of Pediatrics (www.aap.org/family/carseatguide.htm).
• Car Safety Seats and Transportation Safety (Web page), American Academy of Pediatrics (www.aap.org/healthtopics/carseatsafety.cfm).
• Safe Transportation of Children with Special Needs (brochure), American Academy of Pediatrics (www.aap.org/bookstore).

• Births: Final Data for 2005 (report), National Center for Health Statistics (www.cdc.gov/nchs/data/nvsr/nvsr56/nvsr56_06.pdf).
• Guidelines for Perinatal Care, 6th edition (book), American Academy of Pediatrics and American College of Gynecologists and Obstetricians (www.aap.org/bookstore).

• American Academy of Pediatrics, Committee on Fetus and Newborn. Age terminology during the perinatal period. Pediatrics. 2004;114(5):1362-1364. (aappolicy.aappublications.org/cgi/content/full/pediatrics;114/5/1362).
• Engle WA, Tomashek KM, Wallman C, Committee on Fetus and Newborn. “Late-preterm” infants: a population at risk. Pediatrics. 2007;120(6):1390-1401. (pediatrics.aappublications.org/cgi/content/full/120/6/1390).

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2. Luke B, Brown MB. The changing risk of infant mortality by gestation, plurality and race: 1989-1991 versus 1999-2001. Pediatrics. 2006;118(6):2488-2497.  [PMID:17142535]
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14. Watkinson M. Temperature control of premature infants in the delivery room. Clin Perinaol. 2006;33(1):43-53.
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Figure 92-1 Percentage distribution births by gestational age (32-44 weeks): United States, 1990 and 2004. (Martin JA, Hamilton BE, Sutton PD, et al. Births: Final Data From 2004. National Vital Statistics Reports. Vol. 55, no. 1. Hyattsville, MD: National Center for Health Statistics; 2006. Available at: www.cdc.gov/nchs/products/pubs/pubd/hestats/prelimbirths05.htm.)

Figure 92-2 Age terminology during perinatal period.

Figure 92-3 Percentage distribution preterm births, United States, 2004.

Figure 92-4 Distribution of preterm births by gestational age, United States, 2003.

Figure 92-5 Percentage of preterm births: United States, 1990, 2004, and 2005. (Hamilton BE, Martin JA, Ventura SJ. Births: Preliminary Data for 2005. National Vital Statistics Reports. Vol 55. Hyattsville, MD: National Center for Health Statistics; 2006. Available at: www.cdc.gov/nchs/products/pubs/pubd/hestats/prelimbirths05.htm; www.cdc.gov/nchs/products/pubs/hestats/prelimbirths05.htm#ref01. Accessed May 15, 2007.)

Figure 92-6 Babson-Benda growth curve.