Association between the number of pregnancies and chronic kidney disease in Korean women: a population-based cross-sectional study from the Korean Genome and Epidemiology Study-Health Examinee (KoGES-HEXA) cohort.

BACKGROUND: Chronic kidney disease (CKD) is a growing public health burden. Repeated pregnancies exert anatomical and physiological stress on the kidneys; however, the association between number of pregnancies and CKD is unclear. METHODS: This cross-sectional study used data from the Korean Genome and Epidemiology Study-Health Examinee (KoGES-HEXA; 2004-2013). The number of pregnancies was categorized as 0, 1, 2, 3, 4, or ≥5. The primary outcome was CKD, defined as an estimated glomerular filtration rate <60 mL/min/1.73 m2, using the CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) formula, or dipstick proteinuria ≥1+. We evaluated the association between number of pregnancies and CKD and whether it varied by adverse pregnancy outcomes (APOs). RESULTS: We included 100,433 women (age, 52.7 ± 8.0 years [mean ± standard deviation]). Of the parous women (n = 99,654), 3.8% (n = 3,795) had CKD. In the fully adjusted model, women with ≥5 pregnancies had modestly higher CKD odds than women with one pregnancy (odds ratio, 1.20; 95% confidence interval, 1.01-1.43). The association differed by age (p for interaction <0.001), with a significant trend among women aged ≥60 years (p for trend = 0.009). In subgroup analyses, ≥5 pregnancies remained associated with CKD among women without preeclampsia or gestational diabetes mellitus, with no clear evidence of interactions. CONCLUSION: A higher number of pregnancies was modestly associated with a higher prevalence of CKD in Korean women, including those without APO history. Although residual confounding by age and birth cohort cannot be excluded, the number of pregnancies may be relevant to women's long-term kidney health.