Women who have an abnormal glucose tolerance test result during pregnancy but do not develop gestational diabetes still face an increased risk of developing type 2 diabetes later on.
The retrospective study showed that even modestly elevated glucose levels double the risk of diabetes within the next 9 years. “The risk of subsequent diabetes … likely occurs since [they] have an intermediate form of glucose intolerance” with impaired β-cell functioning, said Dr. Darcy B. Carr of the University of Washington, Seattle, and coauthors (Diabetes Care 2008 Jan. 25 [doi 10.2337/dc07–1957
In this retrospective cohort study, the researchers analyzed diabetes risk over a mean 9-year follow-up period in 31,000 women without gestational diabetes who had an oral glucose tolerance test (OGTT) or oral glucose challenge test (OGCT) during their pregnancy. The mean age was 31 years; the median follow-up was 9 years.
They found that the risk of later development of type 2 diabetes rose as the OGCT values rose. Compared with women whose levels were normal, those with glucose levels of 5.4–6.2 mmol/L and 6.4–7.3 mmol/L had double the risk of developing the disease, while those with levels greater than 7.3 mmol/L were three times more likely to do so. Women with no abnormal OGTT values were at no increased risk of developing type 2 diabetes, but those with one abnormal value were twice as likely to do so. These associations remained significant even after controlling for age, primigravidity, and preterm delivery.
The finding is consistent with those from a previous, much smaller longitudinal study that reported higher frequencies of glucose intolerance in women with one abnormal OGTT value.
The authors noted that the study could not control for race, family history, or body mass index—all important factors in assessing diabetes risk. In addition, subsequent diabetes was not systematically assessed, which may introduce bias in those who were selected for testing, they wrote.
They also said their conclusions are not sufficient for them to make any screening or treatment recommendations, adding that, “Whether women who fall within this intermediate range of glucose intolerance during pregnancy may benefit from increased diabetes surveillance as well as lifestyle recommendations proven to reduce the risk of developing diabetes is unknown.”
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