Menstrual, reproductive, and contraceptive factors associated with cervical cancer in women aged ≤35 years: an individually matched case–control study

Objective This study aims to investigate the associations of menstrual, reproductive, and contraceptive characteristics with early-onset cervical cancer among women aged ≤35 years. Methods A hospital-based, individually matched case–control study was conducted at West China Second University Hospital from January 2022 to December 2024. A total of 300 women aged ≤35 years and with histologically confirmed cervical cancer were individually matched 1:1 to 300 screening controls within 0.5 years of age and 7 days of recruitment. Menstrual, reproductive, and contraceptive histories accrued up to 90 days before the index data were collected through standardized interviews and medical record reviews. Separate exposure-specific conditional logistic regression models stratified by matched pair were adjusted for prespecified sociodemographic, behavioral, screening-related, infection-related, and current high-risk human papillomavirus (hrHPV) covariates. The model samples ranged from 189 to 277 matched pairs. Exploratory subgroup analyses assessed effect modification. Results 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. Conclusions Selected menstrual, reproductive, and contraceptive characteristics were associated with early-onset cervical cancer after adjustment for measured confounders and current hrHPV status.