U-shaped association between age at first childbirth and mortality: A prospective cohort study

Objectives: We examined the association between maternal age at first childbirth and death from cardiovascular disease and all-cause mortality in Korean women. Methods: We used data from a community-based cohort with a follow-up of 18 years (2001–2018). Participants were subdivided into three groups according to the tertiles of age at first childbirth [≤ 23 (n=1498), 24 and 25 (n=1033), and ≥ 26 years (n=1513)]. Kaplan–Meier survival analysis was performed to assess CVD mortality rates and all-cause mortality rates. We compared mortality hazard ratios (HRs) using the Cox proportional hazards model and investigated whether hypertension and diabetes mellitus (DM) affected this association using mediation analysis. Results: Participants’ mean ages at first childbirth and at survey entry were 24.7 and 52.4 years, respectively. Age at first childbirth and mortality (CVD and all-cause) showed a U-shaped association. Compared with the group aged 24 and 25 years at first childbirth, the adjusted HRs were significantly higher in the younger and older groups. Hypertension and DM did not mediate the association between maternal age at first childbirth and CVD and all-cause mortality rates. Conclusion: Mothers who had given birth at an early or late age were at greater risk of CVD and all-cause mortality than mothers who had given birth in their mid-20 s. We suggest that further research is needed to determine whether maternal age at first childbirth affects women's health and lifespan.