Table 1_Menstrual, reproductive, and contraceptive factors associated with cervical cancer in women aged ≤35 years: an individually matched case–control study.xlsx

The model samples ranged from 189 to 277 matched pairs. Exploratory subgroup analyses assessed effect modification.</p>Results<p>In the fully adjusted model, menstrual period duration was associated with early-onset cervical cancer, with evidence of nonlinearity (P for nonlinearity <0.001). Each 1-year increase in age at first pregnancy was associated with lower odds (adjusted odds ratio [aOR], 0.717; 95% confidence interval [CI], 0.561–0.917).

Higher odds were associated with greater gravidity (aOR per pregnancy, 2.959; 95% CI, 1.734–5.050), greater parity (aOR per birth, 3.667; 95% CI, 1.886–7.133), and more induced abortions (aOR per event, 2.672; 95% CI, 1.236–5.773). Longer total breastfeeding duration was inversely associated (aOR per 12 months, 0.189; 95% CI, 0.064–0.560), whereas longer cumulative combined oral contraceptive use was positively associated (aOR per 12 months, 1.335; 95% CI, 1.062–1.678).

Age at menarche, menstrual cycle irregularity, ever breastfeeding, categorical combined oral contraceptive status, and other contraceptive methods were not statistically significant after full adjustment. No interaction remained statistically significant after false discovery rate correction.</p>Conclusions<p>Selected menstrual, reproductive, and contraceptive characteristics were associated with early-onset cervical cancer after adjustment for measured confounders and current hrHPV status.</p>