Hydramnios in twin gestations

OBJECTIVE: To estimate the effect of hydramnios on pregnancy outcomes in dichorionic and monochorionic twins. METHODS: This is a retrospective cohort study of women with twin pregnancies who underwent ultrasound evaluation between 1997 and 2010 and delivered liveborn neonates or stillborn fetuses at 24 weeks of gestation or more at a single institution. Hydramnios was defined as a single deepest pocket of amniotic fluid of at least 8 cm, and it was further categorized as mild (8-9.9 cm), moderate (10-11.9 cm), or severe (12 cm or more). The greatest degree of hydramnios identified during pregnancy was used for analysis. Monoamniotic pregnancies and pregnancies complicated by twin-twin transfusion syndrome were excluded. Anomalous neonates and stillborn fetuses were analyzed separately. RESULTS: Of 1,951 twin pregnancies, 1,311 were dichorionic (67%) and 640 were monochorionic (33%). Hydramnios was identified in 348 pregnancies (18%). Major anomalies were more common with increasing hydramnios in both dichorionic and monochorionic twins (P<.001), with anomaly prevalence nearly 20% in cases of severe hydramnios. Severe hydramnios was significantly associated with stillbirth in monochorionic gestations (3 of 11, 27%, P<.001). Hydramnios was not associated with preterm delivery, fetal growth restriction, neonatal intensive care unit admission, or neonatal death in either dichorionic or monochrorionic pregnancies. CONCLUSION: Hydramnios is common in twins, occurring in one of six dichorionic and monochorionic pregnancies. Anomaly prevalence increased with degree of hydramnios; in monochorionic gestations, severe hydramnios was associated with risk of stillbirth. Despite this, adverse outcomes do not appear to be more frequent in the setting of hydramnios in twin getstaions.