In a large population-based cohort study, researchers from the University of Toronto and the Institute for Clinical Evaluative Sciences (ICES) studied data on 435,696 women in Ontario, Canada, who gave birth between April, 1994 and March, 1998. All women were followed until March 31, 2008. The study excluded women with pre-existing diabetes.
As cardiovascular disease is the leading cause of death in Canadian women, it is important to identify early predictors of future vascular risk. While women with gestational diabetes have a higher risk of cardiovascular disease than those without, it previously has not been known whether mild glucose intolerance in pregnancy is associated with heart disease. The study sought to answer this question.
Gestational diabetes is a condition leading to temporarily high blood sugars during pregnancy. It is an important risk factor for future type 2 diabetes. Women are generally screened for gestational diabetes with a glucose challenge test in the late second trimester. If the result is abnormal, they go on to have an oral glucose tolerance test to confirm the diagnosis.
"Women who had an abnormal glucose challenge test but then did not have gestational diabetes had an increased risk of future cardiovascular disease compared to the general population, but a lower risk than women who actually did have gestational diabetes," writes Dr. Baiju Shah, Institute for Clinical and Evaluative Sciences and coauthor.
They suggest that "in women with glucose intolerance during pregnancy, type 2 diabetes and vascular disease may develop in parallel, which is consistent with the "common soil" hypothesis for these conditions."
Current screening procedures for gestational diabetes might also provide a means for the early identification of women who are at risk for developing heart disease later in life.
In a related commentary http://www.cmaj.ca/press/cmaj091396.pdf
, Dr. J. Kennedy Cruickshank and Dr. Moulinath Banerjee of the Manchester Royal Infirmary, University of Manchester, UK write that "what the study by Retnakaran and Shah shows is that we all have a great deal to learn from sub-clinical blood vessel changes in younger women who are likely overweight during pregnancy."
They suggest that diabetes research should focus on the blood vessel rather than glycemia.