Isolated oligohydramnios–should induction be offered after 36 weeks?

Objective: Isolated oligohydramnios (IO) - oligohydramnios in the absence of maternal or gestational comorbidity is debated as an indication for induction of labor. Previous meta-analyses regarding perinatal outcomes of IO at term have yielded conflicting results. We aimed to investigate the neonatal outcomes among gestations with IO delivered at 36°^/7–39^6/7. Methods: The study cohort included all women undergoing a trial of labor between during 2011 and 2019 of a singleton gestation with cephalic presentation between 36°^/7 and 40°^/7. We allocated the study groups into women with IO and those with normal amniotic fluid volume. Neonatal outcomes were compared between the groups and in relation to gestational age and induction of labor. Results: Overall, there were 529/17,709 (3.0%) IO cases. IO was associated with maternal age <25 years (OR [95% CI] 1.62 (1.20–2.20), p =.001). Induction of labor was more common with IO (OR [95% CI] 1.33 (1.05–1.69) p =.01. IO was associated with preterm delivery (OR [95% CI] 1.81 (1.36–2.40), p <.001). The rate of neonatal adverse outcome did not differ between study groups. Overall composite adverse neonatal outcome occurred among 1,399/17,709 (7.9%) deliveries. Adverse neonatal outcome was associated with induction of labor (OR [95% CI] 1.61 (1.40–1.86), p <.001) and low birth weight (OR [95% CI] 7.41 (6.27–8.75), p <.001). When Stratified by gestational age, neonatal adverse outcome did not differ between IO and no IO groups. When examining cases of induction of labor per gestational age, induction of labor at 36 weeks among IO gestations, was associated with adverse neonatal outcome as compared to no IO group (OR [95% CI] 5.7 (1.23–26.3), p =.04). Conclusions: Induction of labor in gestations complicated by IO at 36 weeks gestational age is associated with an increased risk for adverse neonatal outcome. Our study results adds to the current literature regarding outcomes of IO and time of delivery. Synopsis: Induction of labor in gestations complicated by IO at 36 weeks gestational age is associated with an increased risk for adverse neonatal outcome.