Objective  To explore the correlation between age at menarche and age at first sexual behaviors among unmarried women in Anhui province.

  Methods  From the participants of a cohort study (Reproductive Health of Couples of Childbearing Age – Anhui Cohort) conducted during April 2019 – June 2021 in 16 districts of Anhui province, we recruited 28 899 women (aged 18 – 49 years) taking premarital examination for their first marriage. Relevant information of the unmarried women were collected with an on-site self-administered questionnaire survey under the help of interviewers. Chi-square test and multivariate logistic regression model were adopted to explore the correlation between age at menarche and age at first sexual behaviors.

  Results  Earlier menarche (at ages of ≤ 12 years) and later menarche (at ages of ≥ 15 years) were reported by 37.2% and 14.0% of the unmarried women. The reported proportions of the women having their first sex at ages ≤ 14, 15 – 17, 18 – 20, and ≥ 21 years were 0.2%, 4.5%, 26.8%, and 68.4%, respectively. Multivariate logistic regression analysis showed that, after adjusting for potential confounding factors, the women with earlier age at menarche were more likely to have first sexual behavior at ages of ≤ 14 (odd ratio OR = 2.721, 95% confidence interval 95% CI: 1.626 – 4.533), 15 – 17 (OR = 1.645, 95% CI = 1.456 – 1.860), and 18 – 20 (OR = 1.155, 95% CI: 1.088 – 1.227) compared to the women with normal age at menarche; while, the women with later age at menarche were less likely to have first sexual behavior at ages of ≤ 14 (OR = 0.230, 95% CI: 0.054 – 0.979), 15 – 17 (OR = 0.573, 95% CI: 0.465 – 0.707), and 18 – 20 (OR = 0.812, 95% CI: 0.745 – 0.885) compared to the women with normal age at menarche, respectively.

  Conclusion  The age at menarche is significantly associated with the age at first sexual behavior among unmarried women in Anhui province.