Gestational Glucose Intolerance and Risk of Future Diabetes

OBJECTIVE Pregnant individuals are universally screened for gestational diabetes mellitus (GDM). Gestational glucose intolerance (GGI) (an abnormal initial GDM screening test without a GDM diagnosis) is not a recognized diabetes risk factor. We tested for an association between GGI and diabetes after pregnancy. RESEARCH DESIGN AND METHODS We conducted a retrospective cohort study of individuals followed for prenatal and primary care. We defined GGI as an abnormal screening glucose-loading test result at ≥24 weeks’ gestation with an oral glucose tolerance test (OGTT) that did not meet GDM criteria. The primary outcome was incident diabetes. We used Cox proportional hazards models with time-varying exposures and covariates to compare incident diabetes risk in individuals with GGI and normal glucose tolerance. RESULTS Among 16,836 individuals, there were 20,359 pregnancies with normal glucose tolerance, 2,943 with GGI, and 909 with GDM. Over a median of 8.4 years of follow-up, 428 individuals developed diabetes. Individuals with GGI had increased diabetes risk compared to those with normal glucose tolerance in pregnancy (adjusted hazard ratio [aHR] 2.01 [95% CI 1.54–2.62], P < 0.001). Diabetes risk increased with the number of abnormal OGTT values (zero, aHR 1.54 [1.09–2.16], P = 0.01; one, aHR 2.97 [2.07–4.27], P < 0.001; GDM, aHR 8.26 [6.49–10.51], P < 0.001 for each compared with normal glucose tolerance). The fraction of cases of diabetes 10 years after delivery attributable to GGI and GDM was 8.5% and 28.1%, respectively. CONCLUSIONS GGI confers an increased risk of future diabetes. Routinely available clinical data identify an unrecognized group who may benefit from enhanced diabetes screening and prevention.