The purposes of this study were (1) to determine the prevalence of oligohydramnios (amniotic fluid index < 5.0 cm) among fetuses with intrauterine growth restriction (IUGR) and newborns identified as small for gestational age (SGA), and (2) among fetuses with IUGR, to determine the predictive accuracy of amniotic fluid index (AFI) < or = versus > 5.0 cm for adverse peripartum outcomes. This was a retrospective review of high-risk pregnancy that had reliable gestational age (GA) and needed weekly biophysical profile (BPP). Along with 95% confidence intervals (CIs), we calculated the likelihood ratios (LRs) and used guidelines promulgated by Evidence-Based Medicine Working Group. Among the 1859 singletons undergoing BPP, IUGR (estimated fetal weight < 10% for GA) was suspected in 22% (n = 410) and the prevalence of oligohydramnios was 6% (95% CI, 4 to 8%). SGA (birthweight < or = 10%) occurred among 28% (n = 517) of newborns and oligohydramnios was noted in 6% (95% CI, 4 to 8%). Among fetuses with IUGR, the LR of oligohydramnios to predict cesarean delivery for nonreassuring fetal heart tracing was 2.0 (range, 0.8 to 5.0); for newborns small for gestational age, 1.9 (range, 1.2 to 3.1), and for neonatal intensive care unit admission, 1.4 (range, 0.6 to 2.3) More than 90% of patients with IUGR or SGA have AFI > 5.0 cm, and oligohydramnios with IUGR is a poor predictor of peripartum complications.