Amnioinfusion in very early preterm prelabor rupture of membranes (AMIPROM): pregnancy, neonatal and maternal outcomes in a randomized controlled pilot study

Abstract

Objective: To assess short- and long-term outcomes of pregnant women with very early rupture of membranes randomized to serial amnioinfusion or expectant management, and to collect data to inform a larger, more definitive clinical trial.

Methods: This was a prospective non-blinded randomized controlled trial with randomization stratified for pregnancies in which the membranes ruptured between 16 + 0 and 19 + 6 weeks' gestation and 20 + 0 and 23 + 6 weeks' gestation to minimize the risk of random imbalance in gestational age distribution between randomized groups. Intention-to-treat analysis was used. The study was conducted in four UK hospital-based fetal medicine units (Liverpool Women's NHS Trust, St Mary's Hospital Manchester, Birmingham Women's NHS Foundation Trust and Wirral University Hospitals Trust). The participants were women with confirmed preterm prelabor rupture of membranes at 16 + 0 to 24 + 0 weeks' gestation. Women with multiple pregnancy, fetal abnormality or obstetric indication for immediate delivery were excluded. Participants were randomly allocated to either serial weekly transabdominal amnioinfusions if the deepest pool of amniotic fluid was < 2 cm or expectant management until 37 weeks' gestation. Short-term maternal, pregnancy and neonatal and long-term outcomes for the child were studied. Long-term respiratory morbidity was assessed using validated respiratory questionnaires at 6, 12 and 18 months of age and infant lung function test at around 12 months of age. Neurodevelopment was assessed using the Bayley Scales of Infant Development, second edition (BSID-II) at corrected age of 2 years.

Results: Fifty-eight women were randomized to the study. Two babies were excluded from the analysis because of termination of pregnancy for lethal anomaly, leaving 56 participants (28 assigned to serial amnioinfusion and 28 to expectant management) recruited between 2002 and 2009. There was no significant difference in perinatal mortality (19/28 vs 19/28; relative risk (RR) 1.0 (95% CI, 0.70-1.43)) and maternal or neonatal morbidity. The overall chance of surviving without long-term respiratory or neurodevelopmental disability was 4/56 (7.1%); 4/28 (14.3%) in the amnioinfusion group and 0/28 in the expectant group (RR 9.0 (95% CI, 0.51-159.70)).

Conclusions: This pilot study found no major differences in maternal, perinatal or pregnancy outcomes. The study was not designed to show a difference between the groups and the number of survivors was too small to draw any conclusions about long-term outcomes. It does, however, signal that a larger definitive study to evaluate amnioinfusion for improvement in healthy survival is needed. The pilot suggests that, with appropriate funding, such a study is feasible.

Keywords: AMIPROM; amnioinfusion; very early preterm prelabor rupture of membranes.