The Effectiveness of Ultrasound-Indicated Cerclage for the Reduction of Extreme Preterm Birth in Twin Pregnancies with a Short Cervix: a Systematic Review and Meta-Analysis

OBJECTIVE: This study aimed to evaluate the effectiveness of cervical cerclage in women with a twin pregnancy and a midpregnancy asymptomatic short cervix (≤25 mm), in preventing preterm birth and improving neonatal outcomes. DATA SOURCES: Systematic searches were conducted in MEDLINE, Embase, Web of Science, Scopus, and Cochrane Library up to April 17, 2023, updated in September and February 2024. STUDY ELIGIBILITY CRITERIA: Included were randomized controlled trials, cohort studies, and case-control studies comparing cerclage with expectant management in twin pregnancies and an asymptomatic short cervix (≤25 mm). METHODS: Risk of bias was assessed using the Newcastle-Ottawa Quality Assessment Scale and the Risk of Bias 2 tool. Data were analyzed using RevMan 5.4 using a random-effects model. RESULTS: Three randomized controlled trials and 13 cohort studies, involving 696 cerclage patients and 595 controls, were analyzed. Combined randomized controlled trial findings (N=49) found no significant difference in preterm birth occurrence after adjustment for preterm birth history and gestational age. Neonates from cerclage-treated mothers exhibited significantly higher rates of respiratory distress syndrome (adjusted odds ratio, 3.88; 95% confidence interval, 1.09-21.03) and very low birthweight (adjusted odds ratio, 2.22; 95% confidence interval, 1.07-5.73). In contrast, pooled cohort data indicated significantly less preterm birth rates in women with a cerclage: at 34 weeks (relative risk, 0.75; 95% confidence interval, 0.63-0.90), 32 weeks (relative risk, 0.67; 95% confidence interval, 0.49-0.90), and 28 weeks (relative risk, 0.572; 95% confidence interval, 0.39-0.83). Cerclage also reduced risk for infants <1500 >g, respiratory distress syndrome, admission at the neonatal intensive care unit, and sepsis. Women with cervical length(relative risk, 0.88; 95% confidence interval, 0.81-0.94), 34 weeks (relative risk, 0.70; 95% confidence interval, 0.57-0.87), 32 weeks (relative risk, 0.63; 95% confidence interval, 0.50-0.80), and 28 weeks (relative risk, 0.43; 95% confidence interval, 0.32-0.59). Perinatal mortality risk was significant lower in neonates born to mothers with a cerclage. For women with cervical length between 16 and 25 mm, no significant differences in outcomes were observed. CONCLUSION: Based on our meta-analysis, cerclage may benefit women with a twin pregnancy with an asymptomatic midpregnancy short cervix <25 >mm, especially in women with a cervix <15 >mm, by reducing preterm birth and improving neonatal outcomes. However, the differences between randomized controlled trials and recent cohort studies emphasize the need for well-powered randomized controlled trials on neonatal outcomes before introducing cerclage in clinical practice for these women.