(587) The higher preterm birth risk after conization is unaltered by conization-to-pregnancy interval or interventions

This study aimed to assess the effect of cervical conization on the incidence of preterm birth and to determine whether conization-to-pregnancy interval or preventive interventions influence this risk.

Study Design:
This retrospective cohort study included 7,080 primiparous women. The study group included 600 (8.5%) women who had a cervical conization before their first delivery, and the rest served as the control group (6,480 women). Baseline characteristics, pregnancy management, and outcomes were compared between the groups. The study group was further analyzed for the rates of preterm birth (< 37, < 34, and < 32weeks) stratified by the conization-to-pregnancy interval (< 6, 6–11, and ≥12 months) and preventive interventions, including cervical cerclage (early < 16 vs late ≥16 weeks) and progesterone administration

Results:

During pregnancy, the study group demonstrated a higher prevalence of short cervix (15.5% vs 4.0%, p< 0.001), with similar rates of pregnancy complications such as hypertensive disorders (7.0% vs 6.7%, p=0.7) and gestational diabetes (4.5% vs 4.3%, p=0.8) to the control group. The study group had a higher risk of preterm birth < 37 weeks (16.2% vs 10.9%; p< 0.0001), < 34 weeks (6.6% vs 3.4%; p< 0.001), and < 32 weeks (4.2% vs 1.1%; p< 0.001). However, within the conization group, preterm birth rate did not differ by conization-to-pregnancy interval, timing of cerclage, or progesterone initiation (Table 1).

Conclusion:

Prior cervical conization in primiparous women increases the risk of preterm birth, including a two- to four-fold risk at < 34 and < 32 weeks. However, preventive interventions or a longer conization-to-pregnancy interval failed to mitigate this risk. Larger cohorts are warranted to validate this finding further.