Association between sonographic cervical appearance and preterm delivery after a history-indicated cerclage

Objectives - To determine which transvaginal cervical sonographic characteristics are associated with preterm delivery after placement of a history-indicated cerclage. Methods - We conducted a case-control study of all women with a singleton gestation and a history-indicated cerclage placed at a single center between January 1, 2008, and October 1, 2012. Cerclages were placed between 12 and 16 weeks' gestation. Cases were defined as women who delivered before 34 weeks' gestation; controls delivered at or after 34 weeks. Transvaginal cervical characteristics, such as cervical funneling, proximal cervical length, distal cervical length, and total cervical length, obtained between 18 and 24 weeks were compared between the two groups. Bivariable, multivariable, and log rank analyses were performed. Results - A total of 124 women met inclusion criteria, with 17 (14%) delivering before 34 weeks. Cervical funneling, a proximal cervical length of less than 1.5 cm, and a total cervical length of less than 2.5 cm were associated with an increased odds of preterm birth before 34 weeks in the bivariable analysis [odds ratio (OR), 10.9 (95% confidence interval (CI), 2.3-62.8), 2.9 (95% CI, 1.0-8.5), and 4.5 (95% CI, 1.3-16.4), respectively], whereas distal cervical length of less than 1 cm was not significantly associated with delivery before 34 weeks [OR, 3.0 (95% CI, 0.8-11.1)]. In multivariable analysis, only cervical funneling remained associated with preterm delivery before 34 weeks [adjusted OR, 10.6 (95% CI, 2.2-51.5)]. Conclusions - In women with a history-indicated cerclage, cervical funneling is the only independently significant sonographic finding associated with an increased risk of preterm birth before 34 weeks.