Idiopathic Polyhydramnios and Neonatal Morbidity at Term

Objective: Idiopathic polyhydramnios is among the most common etiologies of polyhydramnios. However, conflicting evidence exists regarding the relationship between polyhydramnios and neonatal morbidity. We investigated the association between pregnancies with and without idiopathic polyhydramnios and neonatal morbidity at term. Study Design: This is a retrospective cohort study of singleton, term (i.e., ≥37^0/7 weeks) pregnancies from 2014 to 2018. Pregnancies complicated by fetal anomalies, pregestational diabetes, and multifetal gestation were excluded. Pregnancies complicated by idiopathic polyhydramnios were defined by the deepest vertical pocket (DVP) ≥8 cm or amniotic fluid index (AFI) ≥24 cm after 20 weeks' gestation and were compared with women without polyhydramnios at time of delivery. These groups were matched 1:2 by gestational age within 7 days at delivery and maternal race. The primary outcome was a composite neonatal morbidity (neonatal death, respiratory morbidity, hypoxic-ischemic encephalopathy, therapeutic hypothermia, seizures, and umbilical artery pH < 7.10). Outcomes were compared between pregnancies with and without idiopathic polyhydramnios. Unadjusted and adjusted risk ratios were estimated using multivariable logistic regression. Results: Idiopathic polyhydramnios was diagnosed in 192 pregnancies and were matched to 384 pregnancies without polyhydramnios. After adjustment for obesity, women with pregnancies complicated by idiopathic polyhydramnios had an increased risk of composite neonatal morbidity 21.4 versus 5.5% (adjusted risk ratio [aRR] = 4.0, 95% confidence interval [CI]: 2.3-6.7). Term neonatal respiratory morbidity was the primary driver 20.3 versus 4.2%, (aRR = 4.8, 95% CI: 2.7-8.7) and included higher use of continuous positive airway pressure 19.8 versus 3.4%, p <0.01 and the need for supplemental oxygen at >12 hours of newborn life 6.8 versus 1.8%, p <0.01. Conclusion: Idiopathic polyhydramnios is associated with term neonatal respiratory morbidity at delivery and during the subsequent hours of newborn life, compared with pregnancies without idiopathic polyhydramnios. Further studies are needed to minimize neonatal morbidity at term.