Perinatal Outcomes of Pregnancies with Borderline Oligohydramnios at Term

Introduction: Limited evidence exists on borderline oligohydramnios. Our objective was to determine perinatal outcomes in uncomplicated term pregnancies with borderline oligohydramnios. Methods: This retrospective analysis compared adverse perinatal outcomes among pregnancies during 2018–2022, between those with borderline oligohydramnios defined as amniotic fluid index (AFI) of 5.1–8.0 cm, those with oligohydramnios (AFI ≤5 cm), and those with normal AFI (8.1–25 cm). The latter matched one-to-one to the borderline oligohydramnios group and served as the control group. The outcomes compared included birthweight, cesarean delivery due to fetal distress, the presence of meconium-stained amniotic fluid, Apgar scores, neonatal intensive care unit admission, and the occurrence of small-for-gestational-age (SGA) neonates. Results: During the study period, 140 women had borderline oligohydramnios and 345 had oligohydramnios; the control group included 140 women. Borderline oligohydramnios was associated with increased rates of delivering SGA neonates (adjusted odds ratio [aOR] = 3.6, 95% confidence interval [CI] 1.1–11.6, p = 0.034) and cesarean delivery due to fetal distress (aOR = 3.0, 95% CI 1.1–8.3, p = 0.032). Rates of composite neonatal outcome (including at least one of the following: cesarean delivery due to fetal distress, meconium-stained amniotic fluid, 5-min Apgar score <7, umbilical artery pH <7.15, or neonatal intensive care unit admission) were higher in both the borderline oligohydramnios (20.7%) and oligohydramnios (18.6%) groups compared to the control group (9.3%) (p = 0.019). Conclusions: Pregnancies with borderline oligohydramnios were associated with increased risks of delivering SGA neonates and requiring cesarean delivery due to fetal distress. These findings support considering closer antepartum surveillance for these pregnancies, especially for identifying abnormal fetal growth.