Effectiveness of cervical cerclage in preventing recurrent preterm birth: a retrospective study

Objective: This study aimed to clarify the effectiveness of cervical cerclage in preventing recurrent preterm births. Design: A retrospective study. Setting: The perinatal registration database of the Japan Society of Obstetrics and Gynecology Perinatal Center from 2014 to 2016. Population or Sample: For this study, 6,060 multiparous women with a history of preterm birth were reviewed. After excluding 17 subjects who had unknown indications for cervical cerclage, 6,043 subjects were included in this study. Methods and main outcome measures: The efficacies of elective, ultrasound-indicated, and emergency cerclage as preventive treatments for women with a history of preterm birth were evaluated by comparing the cerclage and non-cerclage cases. Prior to evaluation, a propensity score matching was performed for elective and ultrasound-indicated cerclage patients. Results: Elective cerclage did not reduce the risk of preterm birth in subsequent pregnancies for any of the pregnancy periods (p = 0.413). Similarly, ultrasound-indicated cerclage was ineffective (p = 1.000). In addition, for ultrasound-indicated cerclage, Kaplan-Meier survival curves showed that the risk of a subsequent preterm birth might increase at < 33 weeks of gestation. However, the hazard ratio could not be determined to be statistically significant using the log-rank test at < 28 weeks of gestation. In contrast, emergency cerclage significantly reduced the risk of subsequent preterm birth for all pregnancy periods (p < 0.001). Conclusions: Subsequent preterm births were effectively prevented only in emergency cerclage cases. For elective and ultrasound-indicated cerclage, statistically significant differences in subsequent preterm births were not evident.