Labor Induction at 41⁺⁰ Gestational Weeks or Expectant Management for the Nulliparous Woman: The Finnish Randomized Controlled Multicenter Trial

As gestational age advances in term pregnancies, the risks of neonatal and maternal morbidity increase. Labor induction prior to 41 weeks’ gestation has been shown to decrease the rates of stillbirth and other complications without increases in the rates of cesarean delivery (CD) or costs. A 2020 systematic review and individual participant meta-data analysis found that perinatal outcomes were more favorable when labor was induced at 41 weeks’ versus expectant management at 42 gestational weeks. Studies of nulliparous individuals at ≥39 gestational weeks found lower rates of CD in individuals who underwent labor induction compared with those managed expectantly. However, labor induction in normal term pregnancies is not started until 41 to 42 weeks in many countries, including Finland. The aim of this study was to compare labor induction at 41⁺⁰ weeks and expectation management between 41⁺⁵ and 42⁺² weeks in nulliparous women. This was a parallel, randomized controlled trial with a superiority design, conducted at 6 Finnish hospitals between March 2018 and March 2022. Included were singleton pregnancies for nulliparous individuals ≥18 years of age, with intact amniotic membranes and no pregnancy complications. Excluded were pregnancies with severe fetal malformations, birthweight >4500 g, placenta previa, suspicion of maternal vaginal infection or chorioamnionitis, or maternal HIV and hepatitis B or C. Eligible individuals were randomized at a 1:1 ratio to begin labor induction on the same day or to be managed expectantly until 41⁺⁵ gestational weeks when labor could be induced. The primary outcomes were rates of CD and a composite of adverse neonatal outcomes, including Apgar score <7 at 5 minutes, umbilical artery PH ≤7.05, base excess ≤12.0, and/or admission to the neonatal intensive care unit. Secondary outcomes included maternal hemorrhage, manual removal of a retained placenta, anal sphincter injury, and intrapartum or postpartum infection. A total of 381 individuals were included in the analysis, with 186 in the early induction group and 195 in the expectant management group. The early induction group had a trend toward lower rates of CD than the expectant management group (16.7% vs 24.1%, respectively; relative risk [RR], 0.7; 95% confidence interval [CI], 0.5 to 1.0; P = 0.07), as well as lower rates for operative delivery (30.6% vs 45.6%; RR, 0.7; 95% CI, 0.5 to 0.9; P = 0.003), hemorrhage ≥1000 mL (12.2% vs 20.8%; P = 0.03), and birthweight ≥4000 g (16.8% vs 29.5%; P = 0.004). In the expectant management group, the rate of spontaneous labor onset was 45.6%. There were no perinatal deaths, and 1 individual in the expectant management group experienced eclampsia. In conclusion, the rates of CD and a composite of adverse neonatal outcomes did not significantly differ in nulliparous individuals who underwent labor induction versus those who were managed expectantly. However, offering individuals early induction at 41⁺⁰ weeks of gestation may be beneficial in reducing the rates of operative delivery, hemorrhage, and neonatal weight gain.