Prophylactic Cerclage to Prevent Preterm Birth after Conization: A Cohort Study Using Data from the National Health Insurance Service of Korea

PURPOSE: To investigate potential differences in the frequency of preterm births (PTB) between pregnancies with or without prophylactic cerclage in women with a history of conization. MATERIALS AND METHODS: We identified women who had their first singleton delivery after conization between 2013 and 2018 using records in the National Health Insurance Service of Korea claims database. We only included women who had undergone a health examination and interview within 2 years before delivery. We used timing of maternal serum alpha-fetoprotein (MSAFP) tests to differentiate early (before) from late (after the MSAFP test) cerclage. The frequency of adverse pregnancy outcomes, including PTB, preterm labor and premature rupture of membranes, antibiotics and tocolytics use, cesarean delivery, and number of admissions before delivery, were compared. RESULTS: A total of 8322 women was included. Compared to the no cerclage group (n=7147), the risks of adverse pregnancy outcomes were higher in the cerclage group (n=1175). After categorizing patients with cerclage into two groups, the risk of PTB was still higher in the early cerclage group than in the no cerclage group after adjusting for baseline factors (4.48%, 30/669 vs. 2.77%, 159/5749, odds ratio 2.42, 95% confidence interval 1.49, 3.92). Other adverse pregnancy outcomes were also more frequent in the early cerclage group than the no cerclage group. CONCLUSION: Early cerclage performed before MSAFP testing does not prevent PTB in pregnancy with a history of conization, but increases the risk of adverse pregnancy outcomes, including PTB.