Approximately 7% of all pregnancies are complicated by GDM, resulting in more than 200,000 cases annually. The prevalence may range from 1 to 14% of all pregnancies, depending on the population studied and the diagnostic tests employed.
According to the American Diabetes Association, GDM is defined as any degree of glucose intolerance with onset or first recognition during pregnancy. The definition applies whether insulin or only diet modification is used for treatment and whether or not the condition persists after pregnancy. It does not exclude the possibility that unrecognized glucose intolerance may have antedated or begun concomitantly with the pregnancy.
The new study showed that women who gained 2.0-2.9 BMI (body mass index) units, or 12 to 17 pounds between the first and second pregnancy were over two times more likely to develop GDM in the second pregnancy compared with those whose weight remained stable (plus or minus 6 pounds between pregnancies).
On the filp side, women who lost more than 6 pounds between the first and second pregnancy reduced their risk of developing GDM in the second pregnancy by approximately 50% compared with women whose weight remained stable.
Investigator Samantha Ehrlich, MPH, a project manager at the Kaiser Permanente Division of Research in Oakland, California explained:
"The results also suggest that the effects of body mass gains may be greater among women of normal weight in their first pregnancy, whereas the effects of losses in body mass appear greater among overweight or obese women. Taken together, the results support the avoidance of gestational weight retention and postpartum weight gain to decrease the risk of GDM in a second pregnancy, as well as the promotion of postpartum weight loss in overweight or obese women, particularly those with a history of GDM."
It is important to recognize and treat gestational diabetes as soon as possible to minimize the risk of complications in the baby. In addition, it is important for women with a history of gestational diabetes to be tested for diabetes after pregnancy because of an increased risk of developing type 2 diabetes in the years following delivery.
Unlike pre-gestational diabetes, gestational diabetes has not been clearly shown to be an independent risk factor for birth defects. Birth defects usually originate sometime during the first trimester of pregnancy, whereas GDM gradually develops and is least pronounced during the first trimester.
Studies have shown that the offspring of women with GDM are at a higher risk for congenital malformations. A large case-control study found that gestational diabetes was linked with a limited group of birth defects, and that this association was generally limited to women with a higher body mass index. It is difficult to make sure that this is not partially due to the inclusion of women with pre-existent type 2 diabetes who were not diagnosed before pregnancy.
Sources: Kaiser Permanente and The American Diabetes Association