Perinatal outcome in pregnancies complicated by isolated oligohydramnios diagnosed before 37 weeks of gestation

OBJECTIVE: To analyze pregnancy outcome in cases of isolated oligohydramnios at preterm. METHODS: A retrospective cohort study of singleton pregnancies diagnosed with isolated oligohydramnios at preterm (n = 108). Pregnancy outcome was compared with a matched control group of low-risk preterm pregnancies with normal levels of amniotic fluid in a 3: 1 ratio (n = 324). RESULTS: Pregnancies complicated by isolated oligohydramnios were characterized by a higher rate of preterm deliveries (26.9% vs 12.3%, P < .001), most of which were iatrogenic, and a higher rate of labor induction and cesarean delivery. Neonates with isolated oligohydramnios were characterized by a lower birthweight and a higher rate of neonatal morbidity. These differences were eliminated when the analysis was limited to the subgroup of pregnancies with isolated oligohydramnios that were managed expectantly and delivered spontaneously at term. CONCLUSION: Adverse pregnancy outcome in cases of isolated oligohydramnios diagnosed at <37 weeks appears to be related to a considerable degree to iatrogenic prematurity.