Oligohydramnios is related to adverse perinatal outcomes particularly when associated with fetal growth restriction. The purpose of this study was to delineate predictors of adverse perinatal outcomes in cases of preterm idiopathic oligohydramnios associated with appropriate-for-gestational-age (AGA) fetal biometry. A database of preterm AGA fetuses (< 37 weeks) presenting for evaluation of idiopathic oligohydramnios (defined as an amniotic fluid index [AFI] < 10th percentile) in the third trimester with delivery information and uterine artery Doppler indices (average resistance index [RI] and bilateral notching) available was prospectively collected ( N = 90). AFI and birth weight (BW) percentiles were calculated using standard tables. Chi-square and Student T test were used to evaluate for predictors of adverse perinatal outcomes including BW < or = 10th percentile, stillbirth, neonatal intensive care unit admission, 5-minute Apgar score < 7, preterm delivery < 35 weeks, and preeclampsia. Patients destined to experience poor perinatal outcomes (22%) were demographically similar to those experiencing normal outcomes in terms of maternal age ( P = 0.5), ethnicity ( P = 0.9), body mass index ( P = 0.3), and parity ( P = 0.9). However, at-risk patients were more likely to present with oligohydramnios at an earlier gestational age (GA) than those not at risk (33.0 +/- 3.0 versus 34.4 +/- 2.0 weeks; P = 0.02). There were no differences in perinatal outcomes associated with AFI percentile ( P = 0.9), increased average uterine artery RI ( P = 0.5), bilateral notching ( P = 0.4) or a combination of increased uterine artery RI and bilateral notching ( P = 0.2). Patients with preterm AGA fetuses who present with idiopathic oligohydramnios at an earlier GA are at risk for adverse perinatal outcomes compared with those presenting later in gestation. Sonographic indices, particularly uterine artery Doppler findings, were not found to be useful predictors of adverse outcomes.