Premature rupture of the membranes at <26 weeks' gestation: role of amnioinfusion in the management of oligohydramnios.

OBJECTIVE

We sought to evaluate whether serial amnioinfusions for persistent oligohydramnios can affect the perinatal and long-term outcomes in extreme cases of preterm premature rupture of membranes.

STUDY DESIGN

All singleton pregnancies with preterm premature rupture of membranes at <26 weeks'gestation and lasting >4 days between January 1991 and December 2001 were included. Amniotic fluid volume was assessed as the maximum cord-free pocket with serial ultrasonographic examinations. Consenting women with persistent (>4 days) oligohydramnios (amniotic fluid=2 cm) received serial transabdominal amnioinfusions to maintain an amniotic fluid pocket >2 cm. The pregnancy, neonatal, and long-term neurologic outcomes of the cases that spontaneously maintained a median amniotic fluid pocket >2 cm were compared with those of women with oligohydramnios who underwent amnioinfusion but continued to have persistent oligohydramnios and with those of women in whom oligohydramnios was alleviated. Statistical analysis included the Wilcoxon rank-sum test and the Fisher exact test with a 2-tailed P<0.05 considered significant. Stepwise logistic regression analysis with the Nagelkerke adaptation of the Cox-Snell R2 was performed to assess prenatal predictors of survival in the persistent ologohydramnios group.

RESULTS

Among the 49 women included in the study, 13 (26.5%) did not have oligohydramnios, the neonatal survival rate was 92%, and normal fetal lung development and neurologic outcome were achieved in all survivors. The remaining 36 women had oligohydramnios, and all underwent serial amnioinfusions, which successfully restored a median amniotic fluid pocket >2 cm for =48 hours in 11 (30%) patients. This successful amnioinfusion group was comparable with the persistent oligohydramnios group (n=25) in gestational age at first amnioinfusion (median, 20.2 weeks; range, 16-25.6 weeks; vs median, 20.3 weeks; range, 16.5-24.2 weeks; P=.4), number of amnioinfusions (median, 3; range, 1-9; vs median, 3; range, 1-5; P=.4), and interval between amnioinfusions (median, 6 days; range, 4-14 days; vs median, 8 days; range, 6-43 days; P=.1). However, patients in the persistent oligohydramnios group had a significantly shorter interval to delivery, lower neonatal survival (20%), and higher rates of pulmonary hypoplasia (62%) and abnormal neurologic outcomes (60%) than the patients in the groups in which amnioinfusion was not necessary or was successful (all P=.01). Logistic regression analysis demonstrated that after taking into consideration successful amnioinfusion (P=0.019) and administration of steroids (P=0.022), none of the other variables, including gestational age at delivery, contributed significantly to the prediction of perinatal survival in the persistent oligohydramnios group.

CONCLUSION

Pregnancies with preterm premature rupture of membranes-related oligohydramnios at <26 weeks' gestation in which serial amnioinfusions successfully alleviate oligohydramnios have a perinatal outcome that is significantly better than the outcome in those with persistent oligohydramnios and is comparable with gestations with preterm premature rupture of membranes in which oligohydramnios never develops. In the persistent oligohydramnios group, successful procedures and prenatal administration of corticosteroids are the only independent predictors of perinatal survival.