• Posted January 22, 2026

Fluoridated Water Doesn't Affect Birth Weights, Study Finds

There’s no link between fluoridated water and lower birth weights for newborns, a large-scale U.S. study has concluded.

The results refute allegations that community water fluoridation harms fetal development, researchers wrote Jan. 20 in JAMA Network Open.

“Our findings provide reassurance about the safety of community water fluoridation during pregnancy,” concluded the team led by senior investigator Matthew Neidell, a professor at Columbia University’s Mailman School of Public Health in New York City.

For decades, communities have added fluoride to drinking water to help prevent cavities. And for just as long, opponents have been concerned that the fluoride could be causing developmental harm to children in the womb.

The U.S. Environmental Protection Agency (EPA) is currently reviewing the science regarding the potential health risks of fluoridation, citing an August 2024 report that linked fluoride exposure above 1.5 milligrams per liter with lower IQ in children.

However, that amount of fluoride is double the 0.7 milligrams per liter recommended by the U.S. Public Health Service. The U.S. Centers for Disease Control and Prevention says the recommended level is equal to about three drops of water in a 55-gallon barrel.

For the study, researchers analyzed the staggered rollout of community water fluoridation across U.S. counties between 1968 and 1988.

By the end of 1988, nearly 90% of counties had adopted community water fluoridation, corresponding to roughly half of the U.S. population.

The team compared the presence of water fluoridation to the birth weights of more than 11 million babies born across 67 counties over 21 years.

“Most prior research has examined fluoride exposure using individual-level measures, such as maternal urinary fluoride concentrations during pregnancy,” Neidell said in a news release. “Our study takes a different approach by assessing fluoride exposure at the community level, reflecting real-world population exposure through public water systems.”

Researchers focused on birth outcomes, particularly weight, "which is a widely accepted summary measure of infant health and is predictive of later-life health and human capital,” Neidell said. 

“Our objective was to evaluate whether prenatal exposure to community water fluoridation is associated with adverse birth outcomes,” he added.

Results showed that estimated changes in birth weight were small and not statistically meaningful, ranging from a decrease of 8.4 grams (about .3 of an ounce) to an increase of 7.2 grams (about .25 ounce).

Overall, no evidence was found linking fluoridation to poor birth outcomes, researchers concluded.

“By using a rigorous population-level design, this study contributes to the broader discussion of potential side effects of fluoride exposure and underscores the importance of strong empirical methods when evaluating large-scale public health interventions,” the research team concluded.

More information

The U.S. Centers for Disease Control and Prevention has more on community water fluoridation.

SOURCE: Columbia University, news release, Jan. 20, 2026