Lifetime ovulations and endometrial cancer risk: A systematic review and meta-analysis.

[BACKGROUND] Lifetime ovulatory years (LOY) estimate the period women are exposed to gonadal hormones in their reproductive life. Research on the relationship between endometrial cancer (EC) and lifetime ovulations is limited. This study investigates the association between LOY and EC risk.

[METHODS] Scopus, PubMed/MEDLINE, and Embase were systematically searched through February 8, 2026, to identify studies reporting the association between lifetime ovulations and EC risk. Two independent reviewers screened the records for eligibility, performed quality assessment, and extracted the relevant data, with disagreements resolved by a third senior reviewer. The pooled effect estimate with a 95% confidence interval was calculated using the random-effects and the meta-regression models.

[RESULTS] Eleven articles were included in the meta-analysis, of which 6 reported odds ratios, 3 reported hazard ratios, 1 reported incidence rate ratios, and 1 reported risk ratios. Two studies reporting LOY as a continuous variable were included only in the qualitative review. Higher LOY was associated with increased risk of EC with a pooled effect estimate of 2.73 (95% CI: 2.00-3.71). Women with the highest LOY had 2.07 times the odds of EC than women with the lowest LOY (95% CI: 1.50-2.85). Moreover, the pooled hazard ratio was 5.27 (95% CI: 3.43-8.10). Leave-one-out analysis did not significantly change the pooled estimates.

[CONCLUSIONS] LOY is a risk factor for EC. Further studies with a standard definition of LOY are necessary to assess its association with EC risk more precisely. PROSPERO Registration: 13 September 2025, CRD420251146449.