We conducted a study to evaluate the feasibility and benefits of transabdominal amnioinfusion in preterm premature rupture of membranes with persistent oligohydramnios for the prevention of pulmonary hypoplasia. To this purpose, we designed a cohort study in which the pregnancy outcome of women with rupture of membranes at < or = 25 weeks and persistent (> or = 4 days) oligohydramnios managed with serial amnioinfusions (n = 18) was compared with that of a historic cohort group (controls) with similar characteristics but managed expectantly (n = 16). Pulmonary hypoplasia was diagnosed at birth in the presence of strict radiological and pathological criteria. No amnioinfusion-related complications occurred. The prevalence of pulmonary hypoplasia was significantly lower among the amnioinfused cases compared with the controls (46% [6 of 13] vs 86% [12 of 14], odds ratio [OR] = 0.4, 95% confidence interval [CI] 0.2-0.9), despite a lower gestational age at rupture of membranes in the treated group. Within the group undergoing amnioinfusions, those in which the infused solution was rapidly lost had a higher rate of pulmonary hypoplasia compared with those in which amnioinfusion alleviated oligohydramnios for > 48 hours (considered successful) (0 of 4 vs. 6 of 9, OR = 2.3, 95% CI 1-5.5). Cases of successful amnioinfusion had a longer interval between membrane rupture and appearance of oligohydramnios than those in which the procedure failed to correct oligohydramnios, even though both groups had similar gestational age at appearance of oligohydramnios. This suggests that the rate of loss of amniotic fluid after membrane rupture may predict the rate of loss of the infused solution, and therefore identify a subset of patients who may benefit from the procedure.