13: Management of the Late Preterm Infant

INTRODUCTION

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.

I. BETWEEN 1992 AND 2002 LATE PRETERMS INCREASED FROM 7.3 TO 8.5% OF ALL BIRTHS, REPRESENTING A 16% INCREASE

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.

II. POTENTIAL ETIOLOGIES

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.

III. COMPLICATIONS OF LATE PRETERM BIRTH

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, ...