Diabetic Retinopathy in Parous Women With and Without Previous Gestational Diabetes Mellitus: A Nationwide Register-Based Cohort Study

OBJECTIVE: To investigate previous gestational diabetes mellitus (GDM) as a potential risk factor for diabetic retinopathy (DR) in women with diabetes, including the potential role of GDM severity and hypertension after pregnancy. RESEARCH DESIGN AND METHODS: A nationwide, register-based cohort study included all women giving birth in Denmark in 1997-2018. We defined GDM and DR using ICD-10 codes. GDM severity was a proxy based on insulin treatment during GDM pregnancy. Subsequent diabetes and hypertension were based on ICD-10 codes and/or medication postpregnancy. Statistical analyses included Cox regression. RESULTS: The complete study population comprised 708,250 women. The GDM prevalence was 3.4%, and the overall median follow-up was 12 years. Diabetes developed subsequently in 18,556 women, and DR occurred in 655 of these. In the women who developed diabetes, previous GDM was associated with a threefold higher risk of DR (adjusted hazard ratio [aHR] 3.0 [95% CI 2.6-3.6]). The risk increased with increasing GDM severity (aHRs 5.6 [95% CI 4.5-6.9] and 2.4 [95% CI 2.0-2.9]) in women with previous GDM with and without insulin treatment, respectively, compared with women without previous GDM [reference group]). In women with subsequent hypertension, GDM exposure was associated with a 2.7-fold higher DR risk (aHR 2.7 [95% CI 2.1-3.5]). CONCLUSIONS: This large population-based study identified GDM as a significant risk factor for DR in parous women with diabetes, a risk that increased with increasing GDM severity and postpregnancy hypertension development. On the basis of this study, planning of DR screening strategies should include awareness of GDM history.