There was a time in the late 1990s when it seemed that the author was performing a cerclage every week.
Low-risk women with incidentally discovered short cervices
By 2001, several studies cast doubt on the utility of cerclage among asymptomatic, low-risk patients incidentally found to have short cervices at routine sonography.1,2 But in 2004, a study by Dr Kypros Nicolaides' Fetal Medicine Foundation essentially closed the door on sonographically indicated cerclages in low-risk women.3 These researchers conducted a multicenter, randomized, controlled trial of Shirodkar cerclage (n=127) versus expectant management (n=126) in women with a short (≤1.5 cm) cervix identified at routine transvaginal scanning between 22 and 24 weeks' gestation. Their primary outcome was the frequency of delivery before 33 completed weeks of pregnancy. They found that the frequency of early preterm births was similar in both groups (22% vs 26%, respectively) and that there were no significant differences in perinatal morbidity or mortality between the groups. The authors concluded that among women with an incidentally discovered short cervix, cerclage did not substantially reduce the risk of early preterm delivery.
High-risk women with short cervices on ultrasound
But what about the value of cerclage in high-risk women with prior early preterm births found to have sonographic evidence of significant cervical shortening around 20 weeks? Using multivariate analysis of 4 randomized trials of cerclage in women with a short (<2.5 cm) cervical length for the prevention of preterm birth at less than 35 weeks, Vincenzo Berghella, MD, and colleagues found that cerclage was associated with a reduced prevalence of prematurity primarily in the subgroup of singleton gestations with prior preterm birth (hazard ratio, 0.66; 95% CI, 0.45-0.92).5 These authors found that 7.6 cerclages would be required to prevent 1 such preterm birth. Ironically, among women with twin gestations, cerclage was associated with a significantly higher rate of preterm birth and a trend toward higher perinatal mortality.
The Vaginal Ultrasound Cerclage Trial adds more clarity. In this study, a subset of patients with prior preterm birth at less than 35 weeks had sonographic measurements of their cervices and were randomized to cerclage or no cerclage.6 Of the 831 eligible women who underwent initial sonographic assessment of cervical length, 318 (31%) were found to have a cervical length of less than 2.5 cm, and 302 were randomized to either the no-cerclage (n=153) or cerclage (n=148) group. The occurrence of preterm birth at less than 35 weeks was not significantly different between the 2 groups: 32% in the cerclage group versus 42% in the no-cerclage group (odds ratio [OR], 0.67; 95% CI, 0.42-1.07). However, subgroup analysis indicated that among patients with a cervical length of less than 1.5 cm, there was a significant benefit from cerclage (OR, 0.23; 95% CI, 0.08-0.66), but no benefit was observed in the 1.5 cm to 2.4 cm cervical length stratum. Kaplan-Meier survival analysis also demonstrated a significant beneficial effect of cerclage only in the less than 1.5 cm group.