Artificial sweeteners are quite the paradox: the no-calorie/low-calorie sugar substitutes, designed to help people lose weight and manage diabetes, seem to have the opposite effect in many cases.

Large population studies suggest that frequent consumption of artificial sweeteners may be linked with weight gain, the development of Type 2 diabetes, and greater risk of metabolic syndrome (which can be a precursor to heart disease, stroke, and diabetes).

A large study that followed thousands of residents of San Antonio for an average of 9 years found those who drank more than 21 servings of diet drinks a week were at twice the risk of becoming overweight or obese, and the more diet soda people drank, the greater the risk.

Earlier this year, The New York Times reported on artificial sweeteners and weight gain, and pointed out that while large studies do not necessarily prove cause and effect, many scientists urge caution, saying more research is needed:

They point to animal studies such as those showing that nonnutritive sweeteners alter responses to blood sugar in rats by disturbing the gut microbiota. Others speculate that artificial sweeteners may disrupt the body’s ability to regulate blood sugar by stimulating sweet taste receptors throughout the digestive system or disrupting hormonal and neurobehavioral pathways that control hunger and satiety.

A new study has revealed yet another potential problem linked to artificial sweeteners: pregnant women who drink artificially sweetened drinks every day may be more likely to give birth to heavier babies who are then more likely to become overweight children.

Researchers at University of Manitoba in Canada studied more than 3,000 pregnant women and their infants. The expectant mothers answered questions about what they ate, and their babies were followed for a year after birth. Mothers who reported consuming more artificial sweeteners – such as Equal (aspartame), Splenda (sucralose), and Sweet’n Low (saccharin) – in beverages were twice as likely to have children that were overweight or obese at one year, compared to women who reported using artificial sweeteners less.

Meghan Azad, assistant professor in pediatrics and child health, who led the study, said:

To our knowledge, we provide the first human evidence that maternal consumption of artificial sweeteners during pregnancy may influence infant BMI.

While this finding does not prove that artificial sweeteners cause obesity in children, it does support previous research that found similar links between the sugar substitutes and health issues, including weight gain. This may be the first human study, however, to investigate how artificial sweeteners during pregnancy might affect weight among infants.

Azad said that the connection remained strong even after she and her team adjusted for the potential effect of other factors on the babies’ weight, such as the mother’s weight, whether she smoked, whether she breastfed her child, and whether the baby was underweight at birth.

She told Time:

Sweeteners aren’t something we really need for any reason, so there’s no harm in avoiding them. This study raises questions about the potential risk to infants now, and that’s something to consider.

Related Reading

Diabetes: What You Need to Know About This Killer Disease

Yikes! 60% of Our Diet Is Made up of This, and It Is Scary Stuff

Pass the Butter, Skip the Sugar: We’ve Been Told Big Fat Lies About Heart Disease