Validating staging criteria for sonographic and physical examination for cervical changes at <24 weeks’ gestation to predict preterm birth

BACKGROUND: Preterm birth represents a significant clinical challenge, and the ability to predict it effectively is a priority in obstetrics. The cervix undergoes specific changes during pregnancy, and staging these changes may offer a valuable predictive model for preterm birth, particularly among women with a midtrimester short cervical length. OBJECTIVE: The study aimed to validate a proposed staging model for asymptomatic women with midtrimester short cervical length and to evaluate its potential for predicting preterm birth. The integration of cervical examination and inspection with cervical length measurement was a novel approach to be assessed. STUDY DESIGN: This was a multicenter, retrospective cohort study that included 925 pregnant women with a singleton fetus and a midtrimester cervical length measurement of ≤25 mm. Cervical conditions were assessed using ultrasonography, a speculum, and a physical examination and were classified into 1 of 5 cervical stages to correlate with the likelihood of preterm birth. Statistical analyses included Kaplan-Meier survival analysis to illustrate the time-to-event characteristics across the 5 stages and density plot evaluation to visualize the distribution of the gestational ages within the stages. RESULTS: The staging model included 5 stages based on cervical length, appearance, and dilatation. Among the 925 participants, 649 were classified as being stage 1, 245 as stage 2, 18 as stage 3, 10 as stage 4, and 3 as stage 5. The observed rates of preterm birth before 37 weeks for individuals classified in stages 1, 2, 3, 4, and 5 were 22.3%, 26.5%, 44.4%, 60%, and 66.7%, respectively (P=.005). The overall observed rates of preterm birth before 28, 32, 34, and 37 weeks’ gestation were 5.5%, 9.9%, 12.2%, and 24.1%, respectively (P=.005). CONCLUSION: This study validated the proposed staging criteria as an effective predictor of preterm birth caused by cervical insufficiency. The results demonstrate a significant increase in the preterm birth rate with advancing stage classification, indicating that the staging effectively stratified women based on their risk for preterm birth and highlighting the potential use for targeted interventions. Implementing these staging criteria can potentially improve the counseling and management of pregnant women at risk for preterm birth.