Ovarian Cancer Risk Varies by Reproductive Factors, Menopause, and Birth Cohort

By: Julia Cipriano, MS, CMPP
Posted: Thursday, February 19, 2026

In a Korean nationwide population-based cohort study of women aged at least 40 years, reproductive factors were linked to ovarian cancer risk, showing distinct patterns by menopausal status and birth cohort. Jin-Hwi Kim, MD, PhD, of The Catholic University of Korea, Seoul, and colleagues stated that their findings, “highlight the need for tailored prevention strategies in aging, low-fertility populations.”

The investigators focused on data from the National Health Insurance Service (NHIS), a single-payer system covering 97% of South Korea’s population. Women aged at least 40 years who underwent NHIS health screening in 2009 and had reproductive, clinical, and other data were included. They were followed until ovarian cancer diagnosis, death, or December 31, 2022, with a mean follow-up of 10.7 years. The final analytic cohort comprised 2,285,774 women (932,637 [40.8%] premenopausal; 1,353,137 [59.2%] postmenopausal), among whom 10,729 ovarian cancer cases were identified.

Early menarche (aged ≤ 12 vs > 16 years) was found to be associated with higher ovarian cancer risk in both premenopausal (hazard ratio [HR] = 1.37) and postmenopausal (HR = 1.24) women. In both groups, parity of two or more births appeared to be associated with lower risk (HR = 0.68 and 0.71). According to the investigators, breastfeeding (HR = 0.86) and oral contraceptive use (HR = 0.75) for at least 12 months were associated with reduced risk in premenopausal women, but no such association was seen in their postmenopausal counterparts. Postmenopausal women were found to have increased risk associated with later menopause (≥ 55 years; HR = 1.36), longer reproductive span (≥ 40 years; HR = 1.21), and hormone replacement therapy use for 2 to 5 years (HR = 1.20). Women in the 1960s birth cohort showed a diminished parity-related reduction in risk (HR = 1.07; P for interaction = .36), coinciding with Korea’s rapid fertility decline.

Disclosure: For full disclosures of the study authors, visit jamanetwork.com.

JAMA Network Open

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