Cesarean delivery may be protective against neoplasms of the uterine cervix in women of childbearing age.

Parity has been reported as a risk factor for cervical cancer. However, no study has investigated the risk of neoplasms of the uterine cervix according to the delivery type. We carried out a retrospective cohort study using nationwide data from the Korean Health Insurance Review and Assessment Database to investigate whether cesarean delivery might be associated with less development of neoplasms of the uterine cervix than a vaginal delivery in women of childbearing age. Women aged 20-44 years, who had undergone vaginal or cesarean deliveries in 2009 were included as subjects. Two individual datasets for carcinoma in situ (CIS) and cancer of the cervix were followed for 8 years until either disease outcomes or 31 December 2016. In total, 260 438 and 132 232 women had undergone vaginal only and cesarean only deliveries, respectively. There were 1505 and 423 new cases of CIS and cervical cancer, respectively, with median follow-up durations of 89.9 and 90.0 months for vaginal delivery and cesarean delivery, respectively. The unadjusted CIS risk ratio for cesarean delivery compared with vaginal delivery was 0.90 [95% confidence interval, (CI), 0.80-1.00]. After adjusting for categorical age, residential area, facility types, and number of visits to obstetrics and gynecology clinics, it was 0.83 (95% CI, 0.75-0.93). The unadjusted and adjusted risk ratios for cervical cancer for cesarean delivery were 0.98 (95% CI, 0.80-1.20) and 0.87 (95% CI, 0.71-1.08), respectively. Cesarean delivery may be more protective against CIS than vaginal delivery in women of childbearing age.