Isolated oligohydramnios in the term pregnancy: is it a clinical entity?

The aim of this study was to test the hypothesis that isolated oligohydramnios in the otherwise normal term pregnancy does not indicate fetal compromise. Women undergoing labor induction for isolated oligohydramnios between 37 and 41-6/7 weeks gestation were matched by gestational age and parity to women with normal amniotic fluid index measurements who presented in spontaneous labor. Pregnancies complicated by hypertension, diabetes, fetal anomalies, or suspected fetal growth restriction were excluded. The primary outcome variable was route of delivery. Secondary outcomes examined included presence of meconium, acidosis, low Apgar score, and NICU admission. A total of 183 women underwent induction for isolated oligohydramnios. When compared to the control group, neonatal outcome measures did not differ in the group induced for oligohydramnios. However, the women who were induced had significantly more cesarean deliveries (15.8% vs. 6.6%, P < 0.01, odds ratio 2.7). The increased need for operative delivery was not attributable to more fetal distress in the oligohydramnios group. We conclude that isolated oligohydramnios in the otherwise normal term pregnancy may not be a marker for fetal compromise, and induction of labor may not be warranted in most cases.