ABSTRACT
BACKGROUND: Cervical cerclage has been used for decades to reduce preterm birth. The Shirodkar and McDonald cerclage are the most commonly used techniques with no current consensus on the preferred technique. OBJECTIVE: To compare the efficacy of the Shirodkar and McDonald cerclage techniques in preventing preterm birth. SEARCH STRATEGY: Studies were sourced from six electronic databases and reference lists. SELECTION CRITERIA: Studies including women with a singleton pregnancy, requiring a cervical cerclage, using either the Shirodkar or McDonald technique that ran comparative analyses between the two techniques. DATA COLLECTION AND ANALYSIS: The primary outcome was preterm birth before 37 weeks, with analyses at 28, 32, 34 and 35 weeks. Secondary data were also collected on neonatal, maternal and obstetric outcomes. MAIN RESULTS: Seventeen papers were included: 16 were retrospective cohort studies and one was a randomised controlled trial. The Shirodkar technique was significantly less likely to result in preterm birth before 37 weeks than the McDonald technique (relative risk [RR] 0.91, 95% CI 0.85-0.98). This finding was supported by a statistically significant reduction in rates of preterm birth before 35, 34 and 32 weeks, PPROM, difference in cervical length, cerclage to delivery interval, and an increase in birthweight in the Shirodkar group. No difference was seen in preterm birth rates <28 weeks, neonatal mortality, chorioamnionitis, cervical laceration or caesarean section rates. The RR for preterm birth prior to 37 weeks was no longer significant when sensitivity analyses were performed removing studies with a serious risk of bias. However, similar analyses removing studies that utilised adjunctive progesterone strengthened the primary outcome (RR 0.83, 95% CI 0.74-0.93). CONCLUSION: Shirodkar cerclage reduces the rate of preterm birth prior to 35, 34 and 32 weeks' gestation when compared with McDonald cerclage; however, the overall quality of the studies in this review is low. Further, large, well-designed randomised controlled trials are required to address this important question to optimise care for women who may benefit from cervical cerclage.
