Isolated Oligohydramnios in Low-risk Pregnancy as a Predictor of Adverse Perinatal Outcome.

Objective : The aim of our study was to assess whether isolated oligohydramnios is associated with adverse perinatal outcomes in low-risk term pregnancy. Methods : Women delivered between March 2001 and July 2003, who underwent ultrasonography from 37 to 41 weeks gestation were analyzed. Women undergoing labor induction for oligohydramnios were matched by gestational age and parity to women with normal amniotic fluid index measurements. Oligohydramnios was defined as an amniotic fluid index (AFI) 5.0 cm regardless of gestational age or an AFI 5th percentile for gestational age. Perinatal outcomes in pregnancies with oligohydramnios were compared with those with a normal AFI. The primary outcome measures were route of delivery, and rate of cesarean delivery for fetal distress. The secondary outcome variables were birth weight, 1-and 5-minute Apgar score of less than 7, presence of meconium staining, and neonatal intensive care unit admission day. Results : A total of 121 pregnant women were evaluated. Among them 21 in oligohydramnios group defined as AFI 5.0 cm and 57 in oligohydramnios group defined as 5th percentile of AFI for gestational age were included. There were no differences between pregnancies with AFI 5.0 cm and those with AFI >5.0 cm with respect to maternal age, parity, nulliparity, gestational age at delivery. The study (N=21) and control groups (N=100) had similar the primary outcome (rate of total cesarean delivery and rate of cesarean delivery for fetal distress) as well as the secondary outcome variables such as birthweight, Apgar score8 day. There were no differences between pregnancies with 5th percentile of AFI for gestational age and those with >5th percentile of AFI with respect to maternal age, parity, nulliparity, and the secondary outcome variables such as birthweight, Apgar score8 day. However, pregnancies with 5th percentile of AFI for gestational age had a significantly higher rate of total cesarean delivery than those with >5th percentile of AFI. Rate of cesarean delivery for fetal distress was not significantly different in the two groups. Conclusion : We demonstrated that oligohydramnios in low-risk term pregnancy does not affect the increased perinatal morbidity and mortality. Therefore, isolated oligohydramnios may not be a marker for fetal compromise in low-risk term pregnancy, and induction of labor may not be warranted in most cases.