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 patie nts with second-trimester ultrasonographic evidence of preterm dilatation o f the internal os treated with cerclage versus those of patients not treate d with cerclage. STUDY DESIGN: From May 1998 through June 1999 patients with ultrasonographi c evidence of preterm dilatation of the internal os between 16 and 24 weeks ' gestation were randomly assigned to receive a McDonald cerclage or no cer clage. Before random assignment all patients underwent amniocentesis and ur ogenital cultures and then received 48 hours of therapy with indomethacin a nd antibiotics. After treatment each patient was followed up as an outpatie nt with bed rest and weekly ultrasonographic evaluation. RESULTS: Of the 61 patients 31 were randomly assigned to cerclage and 30 we re randomly assigned to no cerclage. There were no differences between grou ps with respect to maternal demographic characteristics, risk factors for p reterm birth, cervical measurements, rescue procedures, readmission, chorio amnionitis, and abruptio placentae. The mean gestational age at delivery (3 3.5 +/- 6.3 weeks) and the perinatal death rate (12.9%) in the cerclage gro up 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 g roup. CONCLUSION: Treatment with McDonald cerclage of preterm dilatation of the c ervix detected ultrasonographically during the second trimester did not imp rove perinatal outcomes.