Community water fluoridation not associated with changes in birth weight

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. The results are published in JAMA Network Open.

Community water fluoridation is one of the most widely implemented public health interventions in the United States and has long been promoted as a safe and effective strategy to prevent dental cavities. While its benefits for oral health are well established, recent studies have raised questions about possible unintended effects of fluoride exposure, particularly during prenatal and early-life periods.

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

Matthew Neidell, PhD, professor of Health Policy and Management, Columbia Mailman School of Public Health, and senior author

"We focused on birth outcomes, particularly birth weight, which is a widely accepted summary measure of infant health and is predictive of later-life health and human capital," according to Neidell, who is also a member of the Columbia Center for Environmental Health and Justice in Northern Manhattan and the Earth Institute at Columbia University. "Our objective was to evaluate whether prenatal exposure to community water fluoridation is associated with adverse birth outcomes."

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 over a 21-year period. Birth outcome data were obtained from the National Vital Statistics System's Natality Detail Files, maintained by the National Center for Health Statistics. Information on county-level fluoridation status came from the Centers for Disease Control and Prevention's 1992 Water Fluoridation Census.

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."

Co-authors are Benjamin Krebs, University of Basel; Lisa Simon, Harvard University; Hannes Schwandt, Northwestern University; and Samantha Burn, Imperial College London.

The study is supported by the National Institute on Aging, through the Paul B. Beeson Emerging Leaders Career Development Award in Aging K76AG095036); and the Swiss National Science Foundation Ambizione Grant (PZ00P1_223786).