June 8, 2009 -- Women who drink five or more sugar-sweetened colas per week may be more likely to develop gestational diabetes if they get pregnant, according to a new study.

The study was presented on June 6 in New Orleans at the American Diabetes Association's 69th annual scientific sessions meeting.

Data came from more than 13,400 female U.S. nurses who took part in the Nurses Health Study II. All participants had at least one pregnancy between 1991 and 2001.

While pregnant, most of the women didn't develop gestational diabetes, but 860 of the women did.

Compared to women who reported drinking less than one sugar-sweetened beverage per month, women who reported drinking five or more sugar-sweetened beverages per month were 22% more likely to report gestational diabetes. Colas were the only sugar-sweetened beverages linked to gestational diabetes.

The findings held regardless of other factors including age, race, number of previous pregnancies, physical activity, smoking, alcohol intake, BMI before pregnancy, and total calorie consumption, according to the researchers, who included Liwei Chen, MD, PhD, assistant professor at Louisiana State University's School of Public Health.

In a separate analysis, Chen's team also found that women who reported high consumption of whole fruits and "moderate" consumption of fruit juices before pregnancy were less likely to develop gestational diabetes.

Chen and colleagues aren't saying that sugary colas cause gestational diabetes, or that fruits and fruit juices prevent gestational diabetes. Observational studies like these can show associations, but not cause and effect.