Amnioreduction in emergency cerclage with prolapsed membranes: comparison of two methods for reducing the membranes.

To evaluate the effectiveness of amnioreduction in pregnancies requiring emergency cerclage placement, we performed a retrospective case-control study of all consecutive pregnant women with cervical dilation and effacement with prolapse of the fetal membranes in vagina between 16 and 26 weeks' gestation, who required placement of a McDonald emergency cerclage during the period January 1991-December 1997. Duration of pregnancy prolongation, rate of delivery before 32 weeks, and duration of neonatal hospital stay were compared between women in whom amniochorionic membranes were reduced at the time of cerclage placement using only intracervical Foley balloon catheter (controls; n = 7) and those who in addition underwent amnioreduction to facilitate cerclage placement (n = 9). Statistical analysis utilized Fisher's exact test and Wilcoxon rank sum test. A p value <0.05 was considered significant. There were no procedure-related ruptures of membranes. Gestational age at cerclage and rate of positive cervico-vaginal cultures were not different between the two groups. Gestation was prolonged for a median of 100 days (range 4 to 144 days) in the amnioreduction group and 10 days (2 to 133) among controls (p = 0.3). The rate of delivery before 32 weeks was significantly lower (1/7 vs. 6/8, p = 0.03) and the duration of neonatal hospital admission significantly shorter (median 3 vs. 37 days, p = 0.001) in the amnioreduction group than among controls. The amount of amniotic fluid withdrawn ranged from 220 to 340 mL. These findings suggest that amnioreduction at the time of emergency cerclage placement is associated with a lower rate of extreme prematurity and related neonatal morbidity.