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Pregnant women with mildly abnormal blood sugar levels at higher risk of developing cardiovascular disease

August 24, 2009 Toronto

Gestational diabetes (GDM) affects more than three per cent of pregnant women in Ontario, and they are at increased risk for future diabetes, hypertension, high cholesterol and cardiovascular disease. New research out of the Institute for Clinical Evaluative Sciences (ICES) shows that even women with mild glucose abnormalities in pregnancy who don’t reach the threshold for GDM are at increased risk for cardiovascular disease later in life.

  • To test for gestational diabetes, women receive a glucose challenge test (GCT) in the late second trimester of pregnancy. If the result of this test is abnormal, they go on to have a diagnostic test, called the oral glucose tolerance test (OGTT). If this test does not show gestational diabetes, women are reassured that their glucose levels are normal and that no further testing is needed.
  • However, recent studies have suggested that women who have even mild abnormalities on either the GCT or the OGTT do actually have subtle differences in their metabolism after pregnancy.
  • The study looked at women aged 20-49 without pre-existing diabetes who delivered between April 1994 and March 1998.
  • The women were divided them into three groups: 349,977 women who did not have an OGTT (and so presumably had a normal GCT), 71,831 women who did have an OGTT (and so presumably had an abnormal GCT) but did not have GDM, and 13,388 who had GDM. The women were followed for a median of 12.3 years.
  • The GDM group was 66 per cent more likely than the “normal GCT” group to have a cardiovascular disease event. Importantly, the group with an abnormal GCT but without GDM still had a 19 per cent increased risk of cardiovascular disease.

“These results show that even a mild abnormality in glucose testing during pregnancy is a marker for increased risk of cardiovascular disease later in life. Although we already know that women who’ve had gestational diabetes need to be monitored, the study suggests that even women with mild glucose abnormalities might benefit from increased cardiovascular risk factor surveillance,” says Baiju Shah, ICES researcher.

Author affiliations: ICES (Shah), Mount Sinai Hospital (Retnakaran), Sunnybrook Health Sciences Centre (Shah); Ontario.

The study “Mild glucose intolerance in pregnancy and risk of cardiovascular disease: a population-based cohort study” is in the August 24, 2009 issue of CMAJ.

ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.

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