By David Liu, PHD

Saturday Nov 24, 2012 (foodconsumer.org) -- Nondiabetic pregnant women eating a diet or food with high dietary glycemic index (DGI) while pregnant may increase risk of birth defects, according to a new study in American Journal of Epidemiology.

S.E. Parker and colleagues conducted the study and found high dietary glycemic index associated with drastically increased risk of a number of birth defects including encephalocele, diaphragmatic hernia, small intestinal atresia/stenosis, cleft lip with cleft palate, and anorectal atresia/stenosis.

Pregnancy diabetes and obesity are known risk factors for several birth defects indicating that high plasma blood sugar (hyperglycemia) and high plasma insulin (hyperinsulinemia) can increase risk of birth defects, according to the authors. This association prompted the researchers to conduct the current study to examine how dietary glycemic index during pregnancy affects risk of birth defects among nondiabetic pregnant women.

For the study, Parker et al. analysed data from 53 nondiabetic pregnant women who had birth defects in the National Birth Defects Prevention Study which lasted from 1997 through 2007.

High dietary glycemix index was found associated with 168%, 158%, 197%, 148%, and 37% increased risk for encephalocele, diaphragmatic hernia, small intestinal atresia/stenosis including duodenal atresia/stenosis and atrial septal defect, respectively.

Additionally, nondiabetic pregnant women in the highest quartile of dietary glycemic index were 23% and 40% more likely to have a baby with cleft lip with cleft palate and anorectal atresia/stenosis, respectively.

High dietary glycemic index and obesity were found to have a synergistic effect on the risk of birth defects.

The researchers concluded "High DGI is associated with an increased risk of a number of birth defects under study. Obesity coupled with high DGI appears to increase the risk further for some birth defects."

Dietary glycemic index indicates how fast a food can release glucose.  Foods that release glucose fast such as refined wheat flour or white rice have a relatively high glycemic index. Sugars are foods with a high glycemic index.