Figure 3.

Adjusted probability of preterm birth less than 34 weeks by thickness of suture type and cerclage indication.

Thick cerclage suture is associated with lower probability of preterm birth less than 34 weeks among women with ultrasound- and exam-indicated cerclages, but not for history-indicated cerclages (effect modification p=0.03). Adjusted probabilities were calculated using linear combinations of beta coefficients from the final logistic regression model with cerclage indication as an effect modifier and additional confounders including progesterone use during pregnancy, gestational age at cerclage placement, surgical approach, and attending surgeon years of experience.