This study aimed to determine whether live birth affects the age at menopause (AAM), explore the relationship between different characteristics and AAM, and develop a model to project the AAM in middle-aged women. A cross-sectional study was conducted with 630 postmenopausal women in Cyprus between January 2022 and June 2022. Postmenopausal women between ages 40 and 90 years completed a 90-question questionnaire that assessed reproductive, socio-demographic, familial, lifestyle and newborn/childhood parameters. Linear regression analysis was used to determine the associations related to AAM, which was questioned in the questionnaire. Multiple linear regression analysis was applied to determine the effect of potential associations on AAM. The mean AAM was 48.7 years. In univariate analysis, the strongest associations observed were the positive correlation between AAM and the number of grown-up children and live births. Other reproduction-related parameters were mildly correlated with AAM. In the multivariable analysis, the effect of reproduction became less critical, including live birth. The strongest associations with AAM were the years of marriage before the AAM, relationship quality with the partner, the participant's mother's AAM and the average AAM of any sisters. A formula including parameters strongly associated with AAM contributed to a 26.7% variation in AAM between women (p < 0.001). As the AAM can be determined to an extent, we can separate early and late AAM groups and prepare for the high-risk conditions related to later or earlier AAM to increase longevity.