Gestational Diabetes Ups Risk of Type 2

July 28, 2008 -- Nearly 19% of women who develop gestational diabetes during pregnancy are likely to develop type 2 diabetes after pregnancy, according to a new study.

Researchers say it's understood that gestational diabetes is a risk factor for type 2 diabetes, but until now the magnitude of that risk was unclear.

"In this large, population-based study, we found that diabetes developed within 9 years after the index pregnancy in 18.9% of women with previous gestational diabetes; this rate was much higher than the rate among women without gestational diabetes (2%)," write researcher Denice Feig, MD, of the University of Toronto and colleagues in the Canadian Medical Association Journal.

(Have you been diagnosed with gestational diabetes? Does this run in your family? Talk about it on WebMD's Pregnancy: 2nd Trimester board.)

Gestational Diabetes Risks

The study followed 659,164 pregnant women in Canada who did not have a history of diabetes prior to pregnancy. Of these, 21,823 developed gestational diabetes during pregnancy.

Researchers found the rate of gestational diabetes rose during the nine-year study period form 3.2% in 1995 to 3.6% in 2001.

Meanwhile, the number of women who developed type 2 diabetes after a diagnosis of gestational diabetes rose from 3.7% at nine months after delivery to 18.9% nine years after delivery.

Thanks to its size, researchers say this study allows them to make a more robust estimate of the risk of developing type 2 diabetes after gestational diabetes than in previous studies.

However, they point out that the study did not "assess the effect of ethnicity, obesity and level of fasting glucose during pregnancy, risk factors that are clearly associated with the development of diabetes."

Nevertheless, researchers say this risk estimate should be used by health care professionals in counseling pregnant women and targeting those women at risk for type 2 diabetes for screening and prevention programs.