5 - Prematurity and complications of labor and delivery

Summary

Introduction

Prematurity is a major contributor to perinatal morbidity and mortality in the USA and around the world. Preterm birth is officially defined as delivery occurring prior to 37 completed weeks from the first day of the last menstrual period. The term “low birthweight” is used to describe infants weighing less than 2500 g at birth. This includes neonates who are born after 37 weeks gestational age, of which approximately one-third are in the category of “growth restriction.” This group of neonates is distinct from the group of premature infants, and is the subject of another chapter (see Chapter 7). The discussion in this chapter will be confined to the preterm fetus, that which is delivered between viability (23–24 weeks) and 37 completed weeks of gestation.

Complications of labor and delivery in both preterm and term gestations have been implicated in adverse neonatal outcomes. Traditionally, cerebral palsy and “brain damage” have been linked to intrapartum events that resulted in “birth asphyxia” and subsequent neurologic damage. This association has continued to be proposed despite the fact that current evidence suggests that only about 10% of patients with cerebral palsy, about 1–2 per 10,000 births, experience serious birth asphyxia. Most studies in this field refer to the term fetus. The preterm neonate has its own unique complications and resultant sequelae.