Abstract
BACKGROUND: To explore associations of birth interval, age at first birth (AFB), age at last birth (ALB) with prevalence of osteoarthritis (OA) in United States (U.S.) postmenopausal women with two deliveries. METHODS: Cross-sectional analysis of 3088 postmenopausal women with two deliveries from the National Health and Nutrition Examination Survey (1999-2018). Weighted multivariable logistic regression, subgroup analysis and restricted cubic spline (RCS) models were used to examine association of reproductive factors (birth interval, AFB and ALB) with OA risk. RESULTS: The prevalence of OA was 30.6%. According to RCS, we found the U-shaped relationships were observed between AFB, ALB, birth interval and risk or OA in postmenopausal women. 24-25 years for AFB, 25-30 years for ALB, and 4-6 years for birth interval were associated with lowest OA risk. These associations persisted across various subgroups. CONCLUSIONS: AFB, ALB and birth interval shown the U-shaped associations with OA prevalence in postmenopausal women with two deliveries. These findings highlight the potential long-term impacts of reproductive history on musculoskeletal health and may inform strategies for OA prevention in U.S. postmenopausal women.