Clinical Characteristics Associated With Very Preterm Delivery Despite Transabdominal Cerclage: A Cohort Study

OBJECTIVE: To identify factors associated with unsuccessful transabdominal cerclage (TAC) insertion, defined as delivery before 32 weeks, including maternal demographics, preterm birth risk factors, operative details (laparoscopic or open, pre-pregnancy or during pregnancy) and subsequent cervical length. DESIGN: Observational cohort study. SETTING: A tertiary-level London hospital. SAMPLE: Women who underwent TAC between 2011 and 2024 and consented to inclusion in the Preterm Clinical Network (PCN) Database. METHODS: Data were collected from the PCN database and maternity records. MAIN OUTCOME MEASURES: Characteristics of women delivering before versus after 32 weeks were compared using student's t-test where data were continuous and chi-squared where data were categorical (SPSS version 29.0). RESULTS: Among 125 pregnancies following TAC, eight (6.4%) delivered before 32 weeks. Previous trachelectomy was strongly associated with preterm delivery (p < 0.0001). Mean cervical length differed significantly between groups: first trimester (19.3 mm vs. 33.8 mm, p < 0.001) and second trimester (18.8 mm vs. 31.9 mm, p < 0.001). Of 30 women with prior pregnancies using the same TAC, 80% (24/30) achieved at least one term birth and 13.3% (4/30) had two or more term deliveries. CONCLUSION: TAC is highly effective, with over 90% of women delivering beyond 32 weeks. Factors linked to unsuccessful TAC include prior trachelectomy and short cervical length in early pregnancy. Effectiveness persists across subsequent pregnancies, with many women achieving multiple term births using the same TAC.