Objective: To develop a model for identifying women receiving cervical cerclage at risk for spontaneous preterm birth <32 weeks.
Study design: Retrospective cohort study of high-risk patients based on past obstetric history. Our inclusion criteria involved all patients with singleton gestation who received cerclage between 10 and 24 weeks. They were evaluated for the risk factors associated with preterm birth <32 weeks. Risk factors evaluated include: indication for cerclage, gestational age at cerclage placement, cervical length prior to cerclage, timing of cerclage (emergency or elective) and route of cerclage (abdominal or vaginal). Univariable and multivariable analyses were used to determine the risk factors associated with preterm birth. A risk-scoring model was developed for the prediction of preterm birth <32 weeks in women receiving cerclage.
Results: We identified 256 women receiving cerclage that met our inclusion criteria. Preterm births <32 weeks occurred in 51 (20%). Multivariable analysis revealed a cervical length <25 mm, a history of cone biopsy and emergency cerclage to be significant risk factors associated with preterm birth <32 weeks. The sensitivity, specificity, positive and negative predictive values of the best model for predicting spontaneous preterm birth <32 weeks in women with cerclage are 80%; 96%; 82% and 95%, respectively.
Conclusion: The presence of a short cervical length, a history of cone biopsy and emergency cerclage were associated with preterm birth <32 weeks. Our model had a high sensitivity for identifying women who may benefit from a closer surveillance.