McDonald vs. Shirodkar cerclage for the prevention of preterm birth in patients with obesity

Objectives Transvaginal cervical cerclage is a common intervention to prevent preterm birth in high-risk patients. This study aimed to compare McDonald and Shirodkar cerclage techniques in preventing preterm birth among patients with obesity, a group at increased risk for adverse pregnancy outcomes. Methods This was a retrospective study of singleton pregnancies complicated by pre-pregnancy obesity (BMI≥30 kg/m 2 ) and transvaginal cerclage placement between 2018 and 2023 within a large health system in New York. The primary exposure was type of cerclage, McDonald or Shirodkar. Primary outcomes were preterm birth <37 weeks and <34 weeks. Secondary outcomes were spontaneous preterm birth <37 and <34 weeks, and gestational age at delivery. Subgroup analyses were performed by cerclage indication (history-, ultrasound-, or exam-indicated). Multivariate logistic regression and linear mixed model analyses were utilized to evaluate these outcomes while controlling for potential confounders. Results Of 495 patients included, 375 (76 %) underwent McDonald and 120 (24 %) underwent Shirodkar cerclage. In adjusted and unadjusted analyses, there was no significant difference in preterm birth at <37 or <34 weeks (p=0.98 and p=0.30 respectively) or spontaneous preterm birth at <37 or <34 weeks (p=0.75 and p=0.36) between the groups. There was no significant difference in mean gestational age at delivery (36.4 ± 4.3 vs. 35.9 ± 4.7 weeks, p=0.50). Subgroup analyses confirmed similar findings across cerclage indications, though with a benefit for the McDonald technique for ultrasound-indicated cerclages (36.6 ± 4.2 vs. 35.0 ± 5.1 weeks, p=0.02). Conclusions McDonald and Shirodkar cerclages are equally effective in prolonging pregnancy in patients with obesity.