Pregnant women hoping to avoid gaining weight or developing gestational diabetes may think artificial sweeteners are the answer to their prayers. They are not.

Using sugar substitutes during pregnancy can increase the body mass index (BMI) of babies and raise the odds that children will become overweight.

Infants born to mothers who drank artificially sweetened drinks daily had an increase in BMI and a two-fold increase of being overweight at their first birthday.

Exposure to artificial sweeteners during pregnancy appears to cause infants to have an increased risk of obesity and metabolic disease, according to a new report.

Over 3,000 mothers and their babies in Canada were involved in the study, which found infants' body mass (BMI) during the first year of life was higher if their mothers drank artificially sweetened drinks. Over 25% of the mothers-to-be reported drinking beverages containing artificial sweeteners. Five percent said they consumed them daily.

Babies born to this group had an increase in BMI and were twice as likely to be overweight at their first birthday compared to infants born to mothers who did not consume artificially-sweetened drinks.

The results are the first to show that artificial sweetener consumption during pregnancy may increase the risk of becoming overweight in early childhood.

The study doesn't prove that mothers' consumption of diet drinks causes weight gain in infants and young children, but it suggests that there may be some as yet unrecognized chemical component or additive in sugar substitutes that disrupts metabolism.

With over 20 percent of preschoolers classified as overweight or obese and the widespread use of artificial sweeteners, more research is needed to fully understand the biological mechanisms that may be responsible for the study’s findings. Most health experts believe artificial sweeteners are safe when used in moderation. But other researchers have also found that excessive weight gain during pregnancy is bad for babies and their mothers.

The Food and Drug Administration deems artificial sweeteners to be safe during pregnancy, though women should probably limit their consumption of them and get the advice of a registered dietitian or their physician on specific sugar substitutes, just to be on the safe side.

The study is published in JAMA Pediatrics.