Intrauterine fetal demise increases progressively beyond 37 weeks of gestation. However, neonatal death rates continue to improve up to 39 or 40 weeks of gestation. Previous studies have suggested that elective induction of labor (induced labor in the absence of medical indications) for prolonged pregnancies of more than 42 weeks may reduce perinatal mortality without increasing rates of cesarean delivery. Few well-designed studies have compared maternal and neonatal outcomes among women with prolonged labor undergoing induction with those expectantly managed.
The aim of this retrospective cohort study was to compare the effect of elective induction and expectant management on maternal and neonatal outcomes. Neonatal outcomes examined included perinatal mortality and special care unit admission; maternal outcomes examined included mode of delivery and delivery complications. The study was conducted between 1981 and 2007 at consultant- and midwifery-led obstetric units in Scotland using a validated unselected population database of more than 1.6 million pregnancies. Participants were 1,271,549 women who had singleton deliveries at 37 weeks or more gestation. Neonatal and maternal outcomes of elective induction of labor at each week of gestation (ie, 37, 38, 39, 40, or 41 weeks’ gestation) were compared with those of expectant management (continued pregnancy to either spontaneous labor, induced labor, or subsequent cesarean delivery at a later gestation). The primary outcome measures were extended perinatal mortality, admission of the neonate to a special care unit, mode of delivery, postpartum hemorrhage, and obstetric anal sphincter injury. Multivariable analysis was used to adjust for potential confounding factors, including age at delivery, parity, year of birth, birth weight, deprivation category, and mode of delivery (where appropriate).
Elective induction of labor at each gestational age between 37 and 41 completed weeks was associated with reduced odds of perinatal death compared with expectant management. For example, at 40 weeks’ gestation, the perinatal mortality rate was 0.08% (37/44,764) in the elective induction group and 0.18% (627/350,643) in the expectant management group; the adjusted odds ratio was 0.39, with a 99% confidence interval of 0.24 to 0.63. Although there was no difference in the odds of spontaneous vertex delivery between 37 and 39 weeks’ gestation from elective induction of labor, at 40 and 41 weeks’ gestation, elective induction of labor was associated with an increased chance of a spontaneous vertex vaginal delivery as compared with expectant management. However, compared with expectant management, the odds of neonatal admission to a special care facility were increased with elective induction of labor at 37, 38, 39, and 40 weeks’ gestation, with no difference seen at 41 weeks’ gestation.
These findings suggest that elective induction of labor at term gestation can reduce perinatal mortality without increasing the risk of operative delivery or decreasing the spontaneous delivery rates.