Mild glucose intolerance in pregnancy and risk of cardiovascular disease: a population-based cohort study

Background: Pregnant women commonly receive screening for gestational diabetes mellitus by use of a 50 g glucose challenge test, followed by a diagnostic oral glucose tolerance test for those whose glucose challenge test result is abnormal. Although women with gestational diabetes have an increased risk of cardiovascular disease, it is not known whether mild glucose intolerance during pregnancy is also associated with cardiovascular disease. Thus, we sought to determine whether pregnant women with an abnormal glucose challenge test result but without gestational diabetes have an increased risk of cardiovascular disease. Methods: We conducted a retrospective population-based cohort study that included all women in Ontario aged 20-49 years with live deliveries between April 1994 and March 1998. We excluded women with pregestational diabetes. The population was stratified into 3 cohorts: women with gestational diabetes (n = 13 888); women who received an antepartum oral glucose tolerance test (suggestive of an abnormal result of the glucose challenge test) but who did not have gestational diabetes (n = 71 831); and women who did not receive an oral glucose tolerance test (suggestive of a normal result of the glucose challenge test) (n = 349 977). The primary outcome was cardiovascular disease (admission to hospital for acute myocardial infarction, coronary bypass, coronary angioplasty, stroke or carotid endarterectomy). Results: Compared with women who did not receive an oral glucose tolerance test, women with gestational diabetes and women who received an oral glucose tolerance test but did not have gestational diabetes had a higher risk of cardiovascular disease over 12.3 years of median follow-up (adjusted hazard ratio [HR] for women with gestational diabetes 1.66, 95% confidence interval [CI] 1.30-2.13, p < 0.001; adjusted HR for those with an oral glucose test but not gestational diabetes 1.19, 95% CI 1.02-1.39, p = 0.03). Interpretation: Mild glucose intolerance in pregnancy may be associated with an increased risk of cardiovascular disease.