Could diet soda be fueling the rise of childhood obesity?

A new study of more than 3,000 Canadian children and their mothers finds a strong link between the amount of artificially sweetened beverages the women drank during pregnancy and the body mass index of their babies.

Compared with women who stayed away from the drinks while they were pregnant, those who consumed them on a daily basis were twice as likely to have their babies classified as overweight when they celebrated their first birthday, according to a report published Monday in JAMA Pediatrics.

Researchers also found that when mothers had a daily habit of drinking beverages flavored with artificial sweeteners during pregnancy, their 1-year-olds had BMI z-scores that were significantly higher than those of their counterparts. (The z-score is a statistic that measures how much a child’s BMI deviates from the average for children of the same age and gender.)

However, the researchers could not find any link between consumption of high-calorie sugar-sweetened beverages during pregnancy and the risk that a baby would be overweight at age 1.

“To our knowledge, our results provide the first human evidence that artificial sweetener consumption during pregnancy may increase the risk of early childhood overweight,” wrote the authors of the study, which was led by Meghan Azad of the University of Manitoba in Canada.

All of the mothers in the study completed a food frequency questionnaire detailing the foods and drinks they consumed while they were pregnant. Nearly 90 percent of the babies got checkups one year after they were born.

Among the moms, 30 percent said they drank artificially sweetened beverages while they were pregnant, including 5 percent who said they did so every day. In addition to diet soda, these drinks included coffee and tea sweetened with packets of Equal, Splenda and the like.

When the researchers controlled for differences in the parents’ BMI, they still found a significant correlation between daily consumption of artificially sweetened beverages and their babies’ BMI. After considering the effects on boys and girls separately, they found that the link was only significant in boys.

Researchers noted that their data did not distinguish between different types of artificial sweeteners, nor did they account for artificial sweeteners used in foods.