The Association Between Menarche Age and First Offspring Sex Ratio

Background: Offspring sex ratio (OSR) serves as an important social factor, and various other factors are hypothesized to be associated with it, such as maternal diet, time of ovulation and insemination, environmental phenomena, parental age, and infertility treatment. Objectives: This research was performed to assess the association between mothers’ menarche age, first pregnancy age, and sex ratio of first offspring. Patients and Methods: In this retrospective study, 2,000 Iranian women of reproductive age were recruited to assess their menarche age, first pregnancy age, and first OSR. Results: The mean age of the participants was 29.6± 7.09, their mean menarche age was 13.25± 1.21, and the mean age of their first pregnancy was 23.9± 4.35. Total OSR was 0.932. The OSR (calculated as the proportion of male to female offspring) was higher when the menarche age was younger (P < 0.05). In women of younger pregnancy age, the OSR was higher (P < 0.05). First pregnancy age was younger in women with a menarche age under 13 years (P < 0.05). Conclusions: Women of younger menarche age will have younger first pregnancy ages and a greater chance of having a male first offspring.