Term Idiopathic Polyhydramnios, and Labor Complications.

: Polyhydramnios is associated with an increased risk of various adverse pregnancy outcomes, yet complications during labor have not been sufficiently studied. We assessed the labor and perinatal outcomes of idiopathic polyhydramnios during term labor. : Retrospective cohort study at a tertiary medical center between 2010 and 2014. Women with idiopathic polyhydramnios defined as an amniotic fluid index (AFI) greater than 24 cm or a deep vertical pocket (DVP) > 8 cm (cases) were compared with women with a normal AFI (5-24 cm) (controls). : Descriptive, means ± SDs, medians + IQR. Comparisons: chi-square, Fisher's exact test, Mann-Whitney Test, multivariate logistic models. : During the study period 11,065 women had ultrasound evaluation completed by a sonographer within two weeks of delivery. After excluding pregnancies complicated by diabetes (pre-gestational or gestational), fetal anomalies, IUFD, multifetal pregnancies, elective cesarean deliveries (CD) or missing data, we included 750 cases and 7000 controls. The degree of polyhydramnios was mild in 559 (75.0%) cases (AFI 24-30 cm or DVP 8-12 cm), moderate in 137 (18.0%) cases (30-35 cm or DVP 12-15 cm) and severe in 54 (7.0%) cases (AFI >35 cm or DVP > 15 cm). Idiopathic polyhydramnios was associated with a higher rate of CD 9.3% vs. 6.2%, = 0.004; a higher rate of macrosomia 22.8% vs. 7.0%, < 0.0001; and a higher rate of neonatal respiratory complications 2.0% vs. 0.8%, = 0.0001. A multivariate regression analysis demonstrated an independent relation between polyhydramnios and higher rates of CD, aOR 1.62 (CI 1.20-2.19 = 0.002) and composite adverse neonatal outcome aOR 1.28 (CI 1.01-1.63 = 0.043). Severity of polyhydramnios was significantly associated with higher rates of macrosomia and CD ( for trend <0.01 in both). : The term idiopathic polyhydramnios is independently associated with macrosomia, CD and neonatal complications. The severity of polyhydramnios is also associated with macrosomia and CD.