Early preterm preeclampsia outcomes by intended mode of delivery

The optimal route of delivery in early-onset preeclampsia before 34 weeks is debated because many clinicians are reluctant to proceed with induction for perceived high risk of failure.

Our objective was to investigate labor induction success rates and compare maternal and neonatal outcomes by intended mode of delivery in women with early preterm preeclampsia.

We identified 914 singleton pregnancies with preeclampsia in the Consortium on Safe Labor study for analysis who delivered between 24 0/7 and 33 6/7 weeks. We excluded fetal anomalies, antepartum stillbirth, or spontaneous preterm labor. Maternal and neonatal outcomes were compared between women undergoing induction of labor (n = 460) and planned cesarean delivery (n = 454) and women with successful induction of labor (n = 214) and unsuccessful induction of labor (n = 246). We calculated relative risks and 95% confidence intervals to determine outcomes by Poisson regression model with propensity score adjustment. The calculation of propensity scores considered covariates such as maternal age, gestational age, parity, body mass index, tobacco use, diabetes mellitus, chronic hypertension, hospital type and site, birthweight, history of cesarean delivery, malpresentation/breech, simplified Bishop score, insurance, marital status, and steroid use.

Among the 460 women with induction (50%), 47% of deliveries were vaginal. By gestational age, 24 to 27 6/7, 28 to 31 6/7, and 32 to 33 6/7, the induction of labor success rates were 38% (12 of 32), 39% (70 of 180), and 54% (132 of 248), respectively. Induction of labor compared with planned cesarean delivery was less likely to be associated with placental abruption (adjusted relative risk, 0.33; 95% confidence interval, 0.16-0.67), wound infection or separation (adjusted relative risk, 0.23; 95% confidence interval, 0.06-0.85), and neonatal asphyxia (0.12; 95% confidence interval, 0.02-0.78). Women with vaginal delivery compared with those with failed induction of labor had decreased maternal morbidity (adjusted relative risk, 0.27; 95% confidence interval, 0.09-0.82) and no difference in neonatal outcomes.

About half of women with preterm preeclampsia who attempted an induction had a successful vaginal delivery. The rate of successful vaginal delivery increases with gestational age. Successful induction has the benefit of preventing maternal and fetal comorbidities associated with previous cesarean deliveries in subsequent pregnancies. While overall rates of a composite of serious maternal and neonatal morbidity/mortality did not differ between induction of labor and planned cesarean delivery groups, women with failed induction of labor had increased maternal morbidity highlighting the complex route of delivery counseling required in this high-risk population of women.