A clinical trial of induction of labor versus expectant management in postterm pregnancy. The National Institute of Child Health and Human Development Network of Maternal-Fetal Medicine Units.

OBJECTIVE: Management of the uncomplicated pregnancy prolonged beyond the estimated date of confinement is controversial, particularly when the cervix is unfavorable for induction. The benefit of reducing potential fetal risk with induction of labor must be balanced against the morbidity associated with this procedure. The objective of this study was to compare two strategies for managing postterm pregnancy (i.e., immediate induction and expectant management).

STUDY DESIGN: Four hundred forty patients with uncomplicated pregnancies at 41 weeks' gestation were randomized to either immediate induction of labor (n = 265) or expectant management (n = 175). Patients with expectant management underwent nonstress testing and amniotic fluid volume assessment twice per week. Patients in the induction group underwent induction within 24 hours of randomization. To evaluate the efficacy of intracervical prostaglandin E2 gel, patients in the induction group were randomized in a 2:1 scheme to receive either 0.5 mg prostaglandin E2 gel or placebo gel intracervically 12 hours before induction of labor with oxytocin.

RESULTS: The incidence of adverse perinatal outcome (neonatal seizures, intracranial hemorrhage, the need for mechanical ventilation, or nerve injury) was 1.5% in the induction group and 1% in the expectant management group (p > 0.05). There were no fetal deaths in either group. There were no differences in mean birth weight or the frequency of macrosomia (birth weight > or = 4000 gm) between the two groups (p > 0.05). Regardless of parity, prostaglandin E2 intracervical gel was not more effective than placebo in ripening the cervix. The cesarean delivery rate was not significantly different in the expectant (18%), prostaglandin E2 gel (23%), or placebo gel (18%) groups.

CONCLUSIONS: Adverse perinatal outcome in otherwise uncomplicated pregnancies of > or = 41 weeks is very low with either of the management schemes described. Thus from the perspective of perinatal morbidity or mortality either management scheme is acceptable.