Oral Glucose Tolerance Test Results in Pregnancy Can Be Used to Individualize the Risk of Future Maternal Type 2 Diabetes Mellitus in Women With Gestational Diabetes Mellitus
RESEARCH DESIGN AND METHODS: We conducted a population-based retrospective cohort study of all nulliparous women with a live singleton birth who underwent testing for GDM using a 75g-OGTT in Ontario, Canada (2007-2017). We estimated the incidence rates (per 1000 person years), overall risk (expressed as adjusted hazard ratio [aHR]), and risk at 5-year post the index pregnancy of future maternal T2DM. Estimates were stratified by the type and number of abnormal OGTT values, as well as by the diagnostic criteria for GDM (Diabetes Canada vs. IADPSG criteria).
RESULTS: A total of 55,361 women met the study criteria. The median duration of follow-up was 4.4 (IQR 2.8-6.3, maximum 10.3) years. Using women without GDM as reference (incidence rate 2.18 per 1000py), women with GDM were at an increased risk of future T2DM, with the risk being higher for the Diabetes Canada compared with the IADPSG criteria (incidence rate 18.74 [95%-CI 17.58-19.90] vs. 14.07 [95%-CI 13.24-14.91] per 1000py, respectively). The risk of future maternal T2DM increased with the number of abnormal OGTT values, and was highest for women with 3 abnormal values (incidence rate 49.93 per 1000py; aHR 24.57 [95%-CI 21.26-28.39]). The risk of future T2DM was also affected by the type of OGTT abnormality: women with an abnormal fasting value had the greatest risk while women with an abnormal 2-hour value had the lowest risk for future T2DM (aHR 14.09 [95%-CI 12.46-15.93) vs. 9.22 [95%-CI 8.19-10.37]), respectively). Similar findings to those described above were observed when the risk of T2DM at a fixed time point of 5-years post the index pregnancy was considered as the outcome of interest.
CONCLUSION: In women with GDM, individualized information regarding the future risk of T2DM can be provided based on the type and number of abnormal OGTT values, as well as the diagnostic criteria used for the diagnosis of GDM.