Induction of labor at full-term in pregnant women with uncomplicated singleton pregnancy: A systematic review and meta-analysis of randomized trials.

INTRODUCTION

The lowest incidence of perinatal morbidity and mortality occurs around 39-40 weeks. Therefore, some have advocated induction of uncomplicated singleton gestations once they reach full-term. The aim of the study was to evaluate the risk of cesarean delivery, and any maternal and perinatal effects of a policy of induction of labor in women with full-term uncomplicated singleton gestations.

MATERIAL AND METHODS

We performed an electronic search from inception of each database to August 2018. All results were then limited to randomized trial. No restrictions for language or geographic location were applied. Inclusion criteria were randomized clinical trials of asymptomatic women with uncomplicated, singleton gestations at full-term (ie, between 39 and 40  weeks) who were randomized to either planned induction of labor or control (ie, expectant management). Only trials on asymptomatic singleton gestations without premature rupture of membranes or any other indications for induction evaluating the effectiveness of planned induction of labor in full-term singleton gestations were included. The primary outcome was the incidence of cesarean delivery.

RESULTS

Seven randomized clinical trials, including 7598 participants were analyzed. Three studies enrolled only women with favorable cervix, defined as a Bishop score of ≥5 in nulliparous women or ≥4 in multiparous women. One trial included only women aged 35 years or older. Women randomized to the planned induction of labor, received scheduled induction usually at 39 to 39  weeks of gestation, whereas women in the control group received expectant management usually until 41-42 weeks of gestation, or earlier if medically indicated. Methods of induction usually included cervical ripening, with either misoprostol or Foley catheter, in conjunction with or followed by oxytocin for women with unfavorable cervix, and oxytocin and artificial rupture of membranes for those with favorable cervix. Five trials also used artificial rupture of membranes as a method for induction. Uncomplicated full-term singleton gestations that were randomized to receive induction of labor had similar incidence of cesarean delivery compared with controls (18.6% vs 21.4%; relative risk 0.96, 95% CI 0.78-1.19). Regarding neonatal outcomes, induction of labor at full-term was associated with a significantly lower rate of meconium-stained amniotic fluid (4.0% vs 13.5%; relative risk 0.32, 95% CI 0.18-0.57), and lower mean birthweight (mean difference -98.96 g, 95% CI -126.29 to -71.63) compared with the control group. There were no between-group differences in other adverse neonatal outcomes.

CONCLUSIONS

Induction of labor at about 39 weeks is not associated with increased risk of cesarean delivery.