Increased risk of cardiovascular and renal disease, and diabetes for all women diagnosed with gestational diabetes mellitus in New Zealand-A national retrospective cohort study

Background: Gestational diabetes mellitus increases the risk of developing type 2 diabetes. The aim of this study is to compare cardiometabolic and renal outcomes for all women in New Zealand with gestational diabetes (2001-2010) with women without diabetes, 10-20 years following delivery. Methods: A retrospective cohort study, utilizing a national dataset providing information for all women who gave birth between 1 January 2001 and 31 December 2010 (n = 604 398). Adolescent girls <15 years, women >= 50 years and women with prepregnancy diabetes were excluded. In total 11 459 women were diagnosed with gestational diabetes and 11 447 were matched (for age and year of delivery) with 57 235 unexposed (control) women. A national hospital dataset was used to compare primary outcomes until 31 May 2021. Results: After controlling for ethnicity, women with gestational diabetes were significantly more likely than control women to develop diabetes-adjusted hazard ratio (HR) 20.06 and 95% confidence interval (CI) 18.46-21.79; a first cardiovascular event 2.19 (1.86-2.58); renal disease 6.34 (5.35-7.51) and all-cause mortality 1.55 (1.31-1.83), all p values <.0001. The HR and 95% CI remained similar after controlling for significant covariates: diabetes 18.89 (17.36-20.56), cardiovascular events 1.79 (1.52-2.12), renal disease 5.42 (4.55-6.45), and all-cause mortality 1.44 (1.21-1.70). When time-dependent diabetes was added to the model, significance remained for cardiovascular events 1.33 (1.10-1.61), p = .003 and renal disease 2.33 (1.88-2.88), p < .0001 but not all-cause mortality. Conclusions: Women diagnosed with gestational diabetes have an increased risk of adverse cardiometabolic and renal outcomes. Findings highlight the importance of follow-up screening for diabetes, cardiovascular risk factors, and renal disease.