Induction of Labour Versus Expectant Management for Large-for-Date Fetuses

Abstract

Macrosomia can increase risk of operative vaginal delivery, perineal trauma, shoulder dystocia, and other neonatal morbidities. To reduce these risks, patients can either elect for cesarean delivery or induction of labor that will prevent further fetal growth. In regard to the latter strategy, previous studies have reported increased risk of cesarean delivery without decrease in risk of neonatal trauma. However, these studies were limited by small sample sizes, gestational age (>40 weeks), and use of birth weight (>4000 g) instead of estimated fetal weight. Consequently, the authors of the present study hypothesize that upon addressing these limitations induction of labor would, in fact, decrease risk of major neonatal and maternal morbidities with no significant changes in the risk of cesarean delivery. This was a large, multicenter (19 tertiary-care university hospitals), randomized, unblinded, controlled trial. A total of 818 women with macrosomic fetuses (eligible for the study if estimated weight of fetus was >95th percentile, or 3500 g at 36 weeks, 3700 g at 37 weeks, and 3900 g at 38 weeks) were randomized into 2 groups, the induction-of-labor group (n = 407) and expectant management or control group (n = 411). Authors induced labor between 37 and 38 weeks’ gestation within 3 days of randomization. It is of note that they induced labor in only 89% of the women in the induced-labor group, as the others experienced spontaneous delivery, and so on. The primary outcome was a composite of significant shoulder dystocia, fracture of the clavicle or a long bone, brachial plexus injury, intracranial hemorrhage, or death of the neonate. The secondary outcomes were a range of neonatal and maternal morbidities. Statistical analysis was by intention to treat. Shoulder dystocia and fracture of the clavicle occurred more frequently for neonates in the control group than in the induction-of-labor group (6% vs 2%; risk difference, 4%; P = 0.004). In addition, frequency of primary outcome increased when neonates were 4000 g or greater, especially in the control group (21 vs 5 neonates). No difference was seen in terms of secondary outcomes for the neonates except for phototherapy use, which was higher in the induction group, especially for those randomized before 38 weeks’ gestation (13% induced-labor vs 7% expectant group). In terms of maternal outcomes and morbidities, the incidence of cesarean delivery and operative vaginal delivery did not differ between the 2 groups. However, spontaneous vaginal delivery occurred more often in the induced-labor group than in the expectant group (59% vs 52%). In addition to being unblinded, a limitation of this study was that the sample size was smaller than initially anticipated; authors were intending to recruit 1000 patients, but recruitment was cut short by funding issues. Nevertheless, the findings of this study show that induction of labor for large-for-date fetuses in women between 37 and 39 weeks’ gestation can significantly reduce risk of neonatal shoulder dystocia and bone fracture. There is also increased likelihood of spontaneous delivery without increased risk of cesarean delivery.