13: Management of the Late Preterm Infant

The increasing number of babies who are delivered between 34 and 37 weeks is a vexing problem for pediatric and obstetric practitioners alike. These babies have an increased risk of short-term health problems and long-term health, behavioral, and learning issues. It has been the subject of growing interest and concern that has generated new research into the cause as well as the appropriate management of these patients. The most commonly agreed upon definition of late preterm infants are those born between 34 0/7 and 36 6/7 weeks' gestation. (See Table 5–2.) Older literature refers to these infants as “near term,” suggesting that they are equivalent to term infants. Recently, the consensus is to refer to these infants as “late preterm,” which conveys an appropriate sense of their vulnerability.

They now represent about three-quarters of all preterm births. One study showed that babies born at 34 weeks were 4.6 times more likely to die than those at 40 weeks, which contributes significantly to the neonatal mortality rate.

Although the exact cause of increased late preterm delivery remains elusive, the rate must be rising due to increased medical interventions at or beyond 34 weeks.

1. Preeclampsia. The most common complication of pregnancy occurring in between 6 and 10% of pregnancies and is rising. Studies conflict as to whether the increase in late preterm deliveries is due to preeclampsia.

2. Preterm labor and premature rupture of membranes (PROM). May lead to late preterm delivery but are not currently preventable.

3. Multifetal gestations. These are rising due to advanced parental age from delayed childbearing and assisted reproductive technology (ART). Multiples contribute to late preterm delivery by virtue of earlier gestation at delivery, unique obstetric complications, increased risk of intrauterine growth restriction (IUGR), and preeclampsia. Interventions to prevent preterm delivery in multiples have been ineffective. Refinement in ART leading to decreased numbers of multifetal gestation may help decrease their contribution to late preterm deliveries.

4. Stillbirths. Declined from 14 to 6.7 per 1000 live births since 1970. The annual number of stillborn babies is equivalent to deaths from prematurity and sudden infant death syndrome (SIDS) combined. Current research does not support stillbirth prevention as a cause of late preterm delivery.

1. Respiratory distress syndrome (RDS). In one large study, 21% of babies born at 33 weeks, 7.3% at 35–36 weeks, and 0.6% at 37–42 weeks had RDS. Late preterm infants are deprived of the normal hormonal changes that occur at term and promote the clearance of lung fluid. In the United States, 17,000 infants born at >34 weeks are admitted to neonatal intensive care units (NICUs) annually, accounting for up to one-third of NICU admissions. In one review, 11% of late preterm infants with respiratory failure developed chronic lung disease and 5% died, demonstrating that respiratory complications can be serious in this population.

2. Length of stay. Studies show that late preterm infants have a similar median length of hospital stay as term infants but with wider variability. The most common causes of delayed discharge are jaundice and poor feeding. Late preterm delivery triples the cost of the baby's initial hospital stay.

3. Jaundice. Late preterm infants are at increased risk of hyperbilirubinemia secondary to hepatic immaturity. Late preterms also may have an increased risk of bilirubin-induced neurologic dysfunction (BIND) due to decreased bilirubin binding, as evidenced by the 25% of babies in the Kernicterus Registry who were born late preterm.

4. Poor feeding. Many late preterm babies with poor feeding require a prolonged initial hospitalization. Suck-swallow coordination and intestinal motility remain immature, which impacts their feeding capability. Late preterms also lack the feeding skills to latch properly and the stamina to feed sufficient volumes of breast milk. Therefore, there is an increased risk of lactation failure in late preterm infants and their mothers. Ineffective sucking can lead to delayed milk production. This may require the use of a breast milk pump to stimulate and augment lactogenesis. Special breast-feeding positions, such as the football and cross-cradle holds, or the use of nipple shields may lead to improvements in the effectiveness of latching in this population. At times, spoon feeding or formula supplementation may be necessary. Breast-feeding protocols that are evidence based have been developed by the California Perinatal Quality Care Collaborative (http://www.cpqcc.org/quality_improvement/qi_toolkits/care_and_mangement_of_the_late_preterm_infant_toolkit) and the Academy of Breastfeeding Medicine (http://www.bfmed.org/ace-files/protocol/near_term.pdf). Problems with the adequacy of breast-feeding may persist until these babies reach term equivalent age. Even babies being formula fed may require a nutrient-enriched approach in order to ensure adequate caloric intake.

5. Temperature instability. Hypothermia is more common in late preterm infants due to an immature epidermal barrier, higher surface area–to–body weight ratios, and more frequent delivery room interventions.

6. Hypoglycemia. Hypoglycemia occurs in 10–15% of late preterm infants. This is due to a delay in the activity of hepatic glucose phosphate, which is needed in the final step of gluconeogenesis. Poor intake in late preterm infants further exacerbates gluconeogenesis. Hypoglycemia can occur any time in the first 24 hours. The American Academy of Pediatrics (AAP) has guidelines for the treatment of hypoglycemia in the late preterm infant. See Chapter 62.

7. SIDS and apnea. Immaturity of the autonomic nervous system in late preterm infants elevates the risk of apnea, bradycardia, and acute life-threatening events. Infants born between 33 and 36 weeks are twice as likely to die from SIDS as those born ≥37 weeks.

8. Readmission. Late preterms were almost twice as likely to require readmission to the hospital. Jaundice and infection were the most common diagnoses. The strongest risk factor for readmission was breast-feeding at discharge. Recent studies demonstrated that early follow-up visits or home nursing visits were effective at reducing rates of readmission.

9. Respiratory syncytial virus (RSV) infection. Late preterm infants have an increased susceptibility to RSV infection due to incomplete lung development and impaired immunity from immaturity and the relative lack of passively acquired maternal antibodies. The risk of RSV bronchiolitis in infants born between 32 and 36 weeks is similar to those born before 32 weeks. The risk of hospitalization due to RSV infection is twice as high in late preterm compared to term infants. Late preterms span from 34 0/7 to 36 6/7 weeks, and the AAP recommendations for palivizumab prophylaxis only goes up to 35 weeks only. Late preterm infants from 34 to 35 weeks with risk factors or those with chronic lung disease or congenital heart disease potentially qualify for treatment. The uncomplicated baby born at 34–35 weeks must also have either a sibling <5 years old or be attending day care, according to the AAP guidelines. Since few late preterm infants qualify for palivizumab, precautions such as decreasing contact with sick individuals and good hand washing by those handling these infants are of great importance. See Chapter 125.

10. Long-term outcomes. By comparison, moderately low birthweight infants (1500–2500 g) are more likely than infants >2500 g to have a special health care need, a chronic condition, a learning disability, or attention deficit hyperactivity disorder (ADHD). Moderately low birthweight infants are at increased risk for poor health outcomes.

Iatrogenic prematurity should be prevented by prolonging pregnancy whenever feasible. To that end, the American College of Obstetrics and Gynecology have come out with recommendations that prohibit induction or scheduled repeat cesarean delivery before 39 weeks, to which most hospitals now adhere. Because late preterm infants are at risk for certain medical problems, previously outlined, specific management strategies should be developed for both their initial hospitalization as well as their care after discharge. Early monitoring of respiratory status, temperature, feeding ability, bilirubin, and glucose levels are critical. The AAP has issued specific recommendations for minimum discharge criteria for late preterm infants. In addition to those things performed for term infants, the late preterm infant requires:

1. Accurate gestational age assessment.

2. Individualizing the time of discharge based on the baby's condition with regard to temperature stability and adequacy of feeding.

3. Identification of a medical home following discharge.

4. Normal vital signs for 12 hours before discharge.

5. Passing of one stool spontaneously.

6. The absence of excessive weight loss.

7. Screening for hyperbilirubinemia.

8. A car seat study for apnea, bradycardia, or oxygen desaturation.

9. Formal breast-feeding education when applicable.

10. Discharge follow-up. Strategies should include closer follow-up of issues such as weight gain and development, as well as good family support.