Objective: To determine pregnancy outcome in patients with short cervix on transvaginal ultrasound between 16 and 24 weeks' gestation treated with McDonald cerclage compared to weekly intramuscular injections of 17 alpha-hydroxyprogesterone caproate (17OHP-C).
Methods: From November 2003 through December 2006, asymptomatic, singleton pregnancies were screened with transvaginal ultrasound between 16-24 weeks' gestation. Patients with a cervical length (CL) < or =25 mm were offered enrollment. Patients were randomly assigned to treatment with McDonald cerclage or weekly intramuscular injections of 17OHP-C. The primary outcome was spontaneous preterm birth (PTB) prior to 35 weeks' gestation.
Results: Seventy-nine patients met inclusion criteria; 42 were randomly assigned to the cerclage and 37 to 17OHP-C. Spontaneous PTB prior to 35 weeks' gestation occurred in 16/42 (38.1%) of the cerclage group and in 16/37 (43.2%) of the 17OHP-C group (relative risk, 1.14 95% CI, 0.67, 1.93). A post hoc analysis of patients with a prior PTB showed no difference in spontaneous PTB <35 weeks between groups. A similar analysis of patients with a CL< or =15 mm showed a reduction in spontaneous PTB <35 weeks in the cerclage group (relative risk 0.48, 0.24-0.97).
Conclusion: Women with CL < or =25 mm in the second-trimester appear to have similar risks of delivering prior to 35 weeks' gestation when treated with 17OHP-C or McDonald cerclage. However, cerclage may be more effective in preventing spontaneous PTB in women with CL< or =15 mm.