Is cerclage height associated with the incidence of preterm birth in women with a history-indicated cerclage?

This study was performed to determine if cerclage height is associated with spontaneous preterm birth in patients with a history-indicated cerclage. We performed a retrospective cohort study of women with a history-indicated cerclage. Functional cervical length and the cerclage height (distance from cerclage to the external cervical os) were obtained. The cohort was grouped into thirds, based on cerclage height percentile. Our primary outcome was spontaneous preterm birth <35 weeks. There were 21 women in group 1 (cerclage height <10 mm), 53 in group 2 (cerclage height 10 to 19 mm), and 31 in group 3 (cerclage height ≥20 mm). The rates of spontaneous preterm birth <35 weeks were similar between each group: 24, 17, and 10%, respectively ( P = 0.38). Cerclage height is not associated with a reduction in spontaneous preterm birth for women with a history-indicated cerclage. The association between longer cerclage height and decrease in preterm birth was nonsignificant possibly due to the small sample size.