Transient Idiopathic Polyhydramnios Maternal and Perinatal Outcomes

Objectives To compare maternal and perinatal outcomes in pregnancies with transient and persistent idiopathic polyhydramnios to those with normal amniotic fluid volume. Methods This retrospective cohort study included subjects delivering a singleton pregnancy between January 1, 2015, and June 30, 2020, with sonography >= 26 weeks' gestation demonstrating transient or persistent idiopathic polyhydramnios (amniotic fluid index [AFI] >= 24.0 cm) or normal AFI (referent group). The primary maternal outcome was a composite of spontaneous preterm delivery <37 weeks, cesarean delivery for malpresentation, abnormal labor progress, or nonreassuring fetal status, operative vaginal delivery, hemorrhage requiring transfusion, and umbilical cord prolapse. The primary perinatal outcome was a composite of birthweight >4500 g, fetal or neonatal death, 5-minute Apgar score <7, and neonatal intensive care unit admission for >24 hours. Results Patients with transient polyhydramnios (n = 259) exhibited maternal outcomes similar to those of the referent group (n = 435) but had significantly increased odds for the primary perinatal outcome (odds ratio [OR] 1.70, 95% confidence interval [CI] 1.15-2.53; P = .008) and for birthweight >= 4500 g (OR 8.70, 95% CI 1.89-40.0; P = .005). Persistent polyhydramnios (n = 176) was significantly associated with both the primary maternal (OR 1.93, 95% CI 1.27-2.95, P = .002) and primary perinatal outcome (OR 2.15, 95% CI 1.40-3.30; P < .001), and individually with cesarean delivery for abnormal labor (OR 3.22, 95% CI 1.55-6.68; P = .002) and birthweight >= 4500 g (OR 8.97, 95% CI 1.84-43.6; P = .007). Conclusions Transient idiopathic polyhydramnios does not impact maternal outcomes but is associated with increased odds of newborn birthweight >4500 g. Persistent polyhydramnios is associated with both adverse maternal and perinatal outcomes.