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, investigators reported.
The large retrospective study, published Jan. 25, concluded that even modestly elevated glucose levels double the risk of diabetes within the next 9 years. “The risk of subsequent diabetes … likely occurs since these women have an intermediate form of glucose intolerance” with impaired β-cell functioning, wrote Dr. Darcy B. Carr of the University of Washington, Seattle, and her 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.
The investigators found that the risk of later development of type 2 diabetes rose as the values of the OGCT rose. Compared with women whose levels were normal, women 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 women with levels greater than 7.3 mmol/L were three times more likely to do so. Women with no abnormal values on the OGTT 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 the researchers controlled 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.
Dr. Carr and her colleagues noted that their study could not control for race, family history, or body mass index—all important factors to consider when 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: “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.”