A randomized trial of cerclage versus no cerclage among patients with ultrasonographically detected second-trimester preterm dilatation of the internal os

Objective: The aim of this study was to compare perinatal outcomes of patients with second-trimester ultrasonographic evidence of preterm dilatation of the internal os treated with cerclage versus those of patients not treated with cerclage. Study Design: From May 1998 through June 1999 patients with ultrasonographic evidence of preterm dilatation of the internal os between 16 and 24 weeks’ gestation were randomly assigned to receive a McDonald cerclage or no cerclage. Before random assignment all patients underwent amniocentesis and urogenital cultures and then received 48 hours of therapy with indomethacin and antibiotics. After treatment each patient was followed up as an outpatient with bed rest and weekly ultrasonographic evaluation. Results: Of the 61 patients 31 were randomly assigned to cerclage and 30 were randomly assigned to no cerclage. There were no differences between groups with respect to maternal demographic characteristics, risk factors for preterm birth, cervical measurements, rescue procedures, readmission, chorioamnionitis, and abruptio placentae. The mean gestational age at delivery (33.5 ± 6.3 weeks) and the perinatal death rate (12.9%) in the cerclage group were similar to the mean gestational age at delivery (34.7 ± 4.7 weeks; P = .4) and the perinatal death rate (10.0%; P = .9) in the no-cerclage group. Conclusion: Treatment with McDonald cerclage of preterm dilatation of the cervix detected ultrasonographically during the second trimester did not improve perinatal outcomes. (Am J Obstet Gynecol 2000;183:830-5.)