Matthew Neidell, PhD, discusses community water fluoridation and birth outcomes

As questions continue to surface about the safety of fluoride exposure during pregnancy, a new population-based study published in JAMA Network Open offers important context for clinicians. In an analysis of more than 11 million singleton births across 677 US counties over 2 decades, investigators found no meaningful association between community water fluoridation and birth weight or other adverse birth outcomes.^1,2 To better understand the study’s design, its use of county-level exposure data, and what the findings mean for counseling pregnant patients, we spoke with Matthew Neidell, PhD, professor of health policy and management at Columbia University Mailman School of Public Health and senior author of the study.

Contemporary Pediatrics: What prompted you to examine community water fluoridation specifically in relation to birth weight, and why is birth weight an important outcome for clinicians to consider?

Matthew Neidell, PhD: The big motivation was that fluoride crosses the placenta—we've known that for a while—which means fetuses are actually exposed during pregnancy. And there have been several studies linking higher maternal fluoride levels in urine to lower birth weight. Given how much attention this has gotten, we wanted to take a careful look at that question using a different approach.

Birth weight is a really useful outcome for this kind of research. For one thing, pregnancy gives you a short, well-defined exposure window, and obviously, a huge amount of development happens in those 9 months. Clinically, birth weight is also one of the best predictors we have for both immediate and long-term health outcomes. So if something environmental were affecting fetal development, birth weight is where you'd expect to see it show up.

Contemporary Pediatrics: Your study takes a population-level approach rather than individual fluoride exposure measures—can you explain why this design was important and how it strengthens the findings?

Neidell: Community water fluoridation is a policy that happens at the community level, so it made sense to study it that way. From a policy perspective, what decision-makers and clinicians actually care about is what happens when you introduce fluoridation into a community's water supply, not just the effect on individuals who happen to drink a certain amount.

So our estimates are really an intent-to-treat effect: what happens to birth outcomes when a community adopts fluoridated water, regardless of how much any person actually drinks. That makes the results directly relevant for policy and clinical guidance, because they reflect how the intervention actually works in the real world, not in some idealized scenario.

Contemporary Pediatrics: You analyzed more than 11 million births across counties over two decades. What did this large, longitudinal dataset allow you to assess that prior studies could not?

Neidell: The scale and time span are what really make this design work. Fluoridation was rolled out gradually across locations over many years, and we can exploit that staggered timing as a kind of natural experiment.

Specifically, we compare birth outcomes in the same county before and after fluoridation begins, and then compare that change to counties that haven't fluoridated yet or never will. It's a quasi-experimental design that just isn't feasible with smaller datasets or cross-sectional studies. And it gives us a much clearer picture of what actually changes when fluoridation is introduced—not just correlation, but something closer to causation.

Contemporary Pediatrics: Some recent studies have raised concerns about prenatal fluoride exposure. How do your findings help contextualize or address those concerns for practicing physicians counseling pregnant patients?

Neidell: Our study focuses on birth weight and gestational length, so we can't claim to settle every question about prenatal fluoride exposure. But birth weight is clinically meaningful, and we find no evidence of harm when we look at it using a rigorous design that really tries to isolate cause and effect.

What's interesting is that our results differ from some earlier studies that suggested negative effects. That points to the possibility that those earlier findings were picking up correlations rather than true causal relationships. That should provide some reassurance to clinicians and patients that the risks may have been overstated.

The big unanswered question is whether the same pattern holds for other outcomes, especially IQ, which is understandably what people worry about most. The more careful studies in that area are increasingly suggesting the link between community water fluoridation and IQ is correlational rather than causal, but that's exactly where we need more high-quality evidence.

Contemporary Pediatrics: Based on your results, what should obstetricians, pediatricians, and public health clinicians take away when discussing the safety of fluoridated drinking water during pregnancy?

Neidell: I'd say the takeaway is reassurance grounded in strong evidence. Looking at more than 11 million births with a design that's well-suited to studying policy interventions, we find no meaningful effect of community water fluoridation on birth weight or gestational length. The estimated effects aren't just statistically insignificant, they're also really small in clinical terms.

For clinicians talking with pregnant patients, especially those who might be anxious after seeing alarming headlines, it's reasonable to say that the best population-level evidence we have doesn't support concerns about adverse birth outcomes from fluoridated drinking water.

At the same time, I think it's fair to acknowledge that research on other outcomes is ongoing, and that study design really matters when you're trying to interpret new claims. Not all studies are created equal, and the methods make a huge difference in whether you're seeing correlation or causation.

Disclosure

Neidell reports no relevant disclosures.

References

1. Community water fluoridation not linked to lower birth weight, large US study finds. News release. Columbia University's Mailman School of Public Health. 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. doi:10.1001/jamanetworkopen.2025.54686