Community water fluoridation not associated with adverse birth weight outcomes

Community water fluoridation (CWF) was not associated with meaningful changes in birth weight or other adverse birth outcomes in a large, population-based cohort study spanning more than 2 decades in the United States. The findings, published in JAMA Network Open, suggest that prenatal exposure to fluoridated drinking water does not negatively affect infant birth weight, a widely used marker of newborn health and a predictor of later-life outcomes.^1,2

CWF is among the most widely implemented public health interventions in the United States and has been credited with substantial reductions in dental caries over the past several decades. Despite its established benefits for oral health, concerns have emerged in recent years about potential unintended health effects of fluoride exposure during pregnancy and early life. Much of the prior research in this area has relied on individual-level biomarkers of fluoride exposure, such as maternal urinary fluoride concentrations, with mixed results.

“Most prior research has examined fluoride exposure using individual-level measures, such as maternal urinary fluoride concentrations during pregnancy.,” said Matthew Neidell, PhD, professor of health policy and management at Columbia University Mailman School of Public Health and senior author of the study. “Our study takes a different approach by assessing fluoride exposure at the community level, reflecting real-world population exposure through public water systems.”

The investigators focused on birth weight as the primary outcome, given its established role as a summary indicator of infant health and its association with long-term health and developmental outcomes. “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,” Neidell said. “Our objective was to evaluate whether prenatal exposure to community water fluoridation is associated with adverse birth outcomes.”

To address this question, researchers analyzed the staggered rollout of CWF across US counties between 1968 and 1988. The study included more than 11 million singleton births from 677 counties over a 21-year period. Birth outcome data were obtained from the National Vital Statistics System’s Natality Detail Files, while county-level fluoridation status was drawn from the Centers for Disease Control and Prevention’s 1992 Water Fluoridation Census.

Using an event-study difference-in-differences design, the investigators compared birth outcomes within counties before and after the introduction of CWF, using counties that never fluoridated or had not yet fluoridated as controls. This approach allowed the researchers to account for time-invariant differences between counties and broader temporal trends that could influence birth outcomes.

By the end of 1988, nearly 90% of counties in the dataset had adopted CWF, corresponding to approximately half of the US population. Across all post-adoption periods, changes in birth weight associated with CWF were small and not statistically significant. Estimated changes ranged from a decrease of 8.4 grams to an increase of 7.2 grams, differences that the authors noted were not clinically meaningful. Overall, no evidence was found linking CWF to adverse birth outcomes.

Secondary analyses examined additional outcomes, including low birth weight, gestational length, and prematurity. These analyses similarly showed no statistically significant associations with community water fluoridation. Sensitivity analyses that accounted for alternative exposure thresholds, state-specific trends, and potential changes in population composition produced consistent results.

The authors noted that prior studies reporting associations between fluoride exposure and birth outcomes may have been limited by residual confounding inherent in observational designs. By contrast, the current study’s use of within-county comparisons over time strengthened causal inference and reduced the influence of unmeasured confounders.

“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.”

While the study did not directly examine neurodevelopmental outcomes, the authors suggested that their findings raise broader questions about the reliability of earlier associational evidence linking fluoride exposure to adverse outcomes. They emphasized the need for future research using similarly robust designs to evaluate remaining concerns.

For clinicians counseling pregnant patients, the findings offer population-level evidence that exposure to fluoridated drinking water is not associated with reductions in birth weight or other adverse birth outcomes, supporting the continued use of community water fluoridation as a public health measure.

References

1. Columbia University's Mailman School of Public Health. Community water fluoridation not linked to lower birth weight, large US study finds. Eurekalert. January 20, 2026. Accessed January 22, 2026. https://www.eurekalert.org/news-releases/1113151
2. Krebs B, Simon L, Schwandt H, Burn S, Neidell M. Community Water Fluoridation and Birth Outcomes. JAMA Netw Open. 2026;9(1):e2554686. Published 2026 Jan 2. doi:10.1001/jamanetworkopen.2025.54686