Gestational Glucose Intolerance and Risk of Future Diabetes

Objective: Pregnant individuals are universally screened for gestational diabetes. Gestational glucose intolerance (GGI, an abnormal initial gestational diabetes screening test without a gestational diabetes 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 gestational diabetes criteria. The primary outcome was incident diabetes. We used Cox proportional-hazard 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, 20,359 pregnancies had normal glucose tolerance, 2,943 had GGI, and 909 had gestational diabetes. 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 [95% confidence interval, CI] 2.01[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; gestational diabetes: aHR 8.26[6.49-10.51], p<0.001; each compared to normal glucose tolerance). The fraction of diabetes 10 years after delivery attributable to GGI and gestational diabetes was 8.5% and 28.1%, respectively.

Conclusion:  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.