About 65 percent of the population of the United States drinks tap water with fluoride added. While community water fluoridation is one of the most widely implemented public health interventions in the country—and has long been promoted as a safe and effective strategy to prevent dental cavities—controversy persists about possible unintended effects of fluoride exposure, particularly during prenatal and early-life periods.
Now, a new study from Columbia University Mailman School of Public Health finds that community water fluoridation (CWF) is not associated with significant changes in birth weight—a widely accepted indicator of infant health and a predictor of later-life outcomes. The findings provide reassurance about the safety of fluoridated drinking water during pregnancy.
For their study, published in JAMA Network Open, the researchers analyzed the staggered rollout of community water fluoridation across U.S. counties between 1968 and 1988. The study included over 11 million singleton births across 677 counties.
The analysis compared birth outcomes within counties before and after the introduction of CWF, using counties that never fluoridated—or had not yet fluoridated—as controls. By the end of 1988, nearly 90 percent of counties had adopted CWF, corresponding to approximately half of the U.S. population.
Across all post-treatment periods, estimated changes in birth weight were small and not statistically meaningful, ranging from a decrease of 8.4 grams to an increase of 7.2 grams. Overall, the study found no evidence that community water fluoridation was associated with adverse birth outcomes.
“Our findings provide reassurance about the safety of community water fluoridation during pregnancy,” the researchers said. “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.”
Data from Columbia University’s Mailman School of Public Health