Projecting future prolapse outcomes with induction of labor at 39 weeks: a decision analysis

In 2018, the ARRIVE trial (A Randomized Trial of Induction Versus Expectant Management) concluded that routine induction of labor (IOL) at 39 weeks gestation decreases cesarean delivery risk, with slightly lighter birthweight infants. We debated whether routine IOL would improve, worsen, or not change POP risk compared with expectant management (EM).

We constructed a decision analysis model with a lifetime horizon where nulliparous women reaching 39 weeks underwent IOL or EM. Subsequent vaginal versus cesarean delivery varied based on prior deliveries for up to four births. Subsequent delivery prior to 39 weeks and distribution of gestational age, birthweight, and delivery mode between 24 and 39 weeks was modeled from national data. We modeled increased POP risk with increasing vaginal parity, forceps delivery, and weight of largest infant delivered vaginally, accounting for differential infant weights in each strategy.

IOL and EM have similar population-wide POP risk (15.9% and 15.7% respectively). Among women with only spontaneous vaginal deliveries that reached 39 weeks or beyond, the prevalence of POP was 20% after one delivery and 29% after four deliveries, with no difference between groups. The cesarean rate was lower with IOL (27.8% versus 29.8%). Sensitivity analysis revealed no meaningful thresholds among the variables, supporting model robustness.

While routine induction of labor at 39 weeks results in a meaningfully higher vaginal delivery rate, there was no increase in POP, possibly due to the protective effect of lower birthweight.