Oral Contraceptive Use and Reproductive History in Relation to Metabolic Syndrome Among Women from Korea NHANES 2010-2023

Background/Objectives: This study examined how reproductive factors—such as oral contraceptive (OC), age at menarche, number of pregnancies, and age at first delivery—are related to the risk of metabolic syndrome (MetS) in Korean women aged 30–69, based on their menopausal status. Methods: Data from the Korea National Health and Nutrition Examination Survey 2010–2023 were analyzed, including 31,178 women with complete data. Survey-weighted logistic regression and restricted cubic spline analyses were conducted, adjusting for sociodemographic, lifestyle, and reproductive covariates. Results: OC use was significantly associated with increased MetS risk in both premenopausal (adjusted OR 1.40, 95% CI 1.13–1.72) and postmenopausal women (adjusted OR 1.16, 95% CI 1.03–1.29). This association was primarily driven by elevated blood pressure in both groups and high triglycerides in postmenopausal women. Other reproductive factors, including age at menarche, number of pregnancies, and age at first delivery, showed no significant nonlinear associations with MetS risk. Established risk factors such as older age, higher BMI, smoking, and high-risk drinking were confirmed. Strength exercise was inversely associated with MetS in postmenopausal women. Conclusions: OC use is linked to higher MetS risk, particularly through blood pressure and triglyceride elevations. Other reproductive factors showed limited association. These findings underscore the importance of considering OC use in metabolic risk assessments and highlight potential benefits of lifestyle interventions.