Manifest diabetes after gestational diabetes: a double-cohort, long-term follow-up in a Danish population

Purpose The aim was to follow-up two cohorts of women with GDM to investigate the incidence and time of diagnosis of manifest diabetes mellitus (DM) postpartum and identify the risk factors for diabetes in our population. Methods A follow-up study on two independent cohorts having oral glucose tolerance test (OGTT) in 1991/1992 and 2011–2016: Cohort 1 consisted of 406 women including 54 with GDM and 352 with a non-GDM OGTT-test and cohort 2 had 433 women diagnosed with GDM. The first cohort had nearly 25 years of follow-up and gave information on magnitude, conversion rate and type of diabetes manifestation. The second cohort was started recently to evaluate whether newer diagnostic criteria and baseline information on the old cohort are still valid for prediction of diabetes risk. Results The risk of manifest diabetes in cohort 1 at the end of follow-up was six times higher in women with previous GDM compared with non-GDM (RR = 6; 95% CI 4–11). We observed a 70% diabetes rate 25 years after pregnancy. Only family history of diabetes in cohort 2 was associated with conversion to manifest diabetes ( p = 0.002), also after adjustment for age, BMI, non-Danish origin and smoking during pregnancy ( p