Predictors of Spontaneous Preterm Birth Among Pregnant Women With a History of Cervical Conization

Objective To explore the predictors of spontaneous preterm birth (PTB) among pregnant women with a history of cervical conization. Methods This retrospective cohort study included pregnant women with a history of conization who visited a tertiary perinatal center before 20 weeks of gestation between 2013 and 2022. Exclusion criteria were cerclage before 24 weeks of gestation, premature rupture of membranes or delivery before 24 weeks of gestation, multiple pregnancies, fetal death, and major fetal anomalies. Multivariate logistic regression analysis was performed to examine the associations between spontaneous PTB before 37 weeks of gestation and variables, including previous spontaneous PTB or second-trimester loss, in vitro fertilization (IVF), pre-pregnancy body mass index, current smoking status, and mid-trimester cervical length (CL). The spontaneous PTB rates among groups stratified by independent predictors were calculated. Results The final analysis included 119 women. Of these, 16 (13.4%) had spontaneous PTB. Multivariate logistic regression analysis revealed that IVF [adjusted odds ratio (OR) = 4.5; 95% confidence interval (CI): 1.2-15.9; p = 0.021] and CL (adjusted OR per 1 mm increment = 0.88; 95% CI: 0.82-0.94; p < 0.001) were significant predictors of spontaneous PTB. The incidence of spontaneous PTB in women who conceived by IVF and/or had a shortened CL<25 mm was 31.1% (14/45), whereas women who did not undergo IVF or had a shortened CL had a lower incidence of 2.7% (2/74). Conclusion Conception by IVF and a shortened CL are significant predictors of spontaneous PTB in women with a history of conization.