TOPLINE:

Analysis of more than 11.4 million births across 677 US counties revealed community water fluoridation (CWF) had no association with changes in birth weight or other birth outcomes. The findings from this 21-year cohort study provide reassurance about CWF safety during pregnancy.

METHODOLOGY:

• A cohort study analyzed 11,479,922 singleton births across 677 counties (408 treated, 269 never treated) in the US from January 1968 to December 1988, with data aggregated to the county-month level.
• The primary outcome measure was change in mean birth weight, whereas secondary outcomes included low birth weight (< 2500 g), gestational length, and prematurity (< 37 weeks’ gestation).
• Analysis utilized an event-study difference-in-differences approach comparing within-county changes before and after CWF introduction, using never-treated or not-yet-treated counties as controls.
• Population exposure to CWF was measured through CDC Fluoridation Census data as the population-weighted share of county residents served by fluoridated water.

TAKEAWAY:

• No significant association was found between CWF and birth weight (difference-in-differences estimate, -0.53; 95% CI, -4.75 to 3.70; P = .81)
• Event-study estimates showed no discernible pretreatment trends and no significant changes following CWF adoption, with estimates for mean difference ranging from -8.44 g (95% CI, -20.41 to 3.53) to 7.20 g (95% CI, -5.45 to 19.85)
• Secondary outcomes including low birth weight, gestational length, and prematurity showed no significant associations with CWF exposure.
• Sensitivity analyses incorporating state-specific time trends and alternative exposure thresholds supported the primary findings.

IN PRACTICE:

“These findings provide reassurance about the safety of CWF during pregnancy and underscore the value of rigorous causal designs in evaluating potential adverse effects of public health interventions,” the authors of the study wrote.

SOURCE:

The study was led by Benjamin Krebs, PhD, Faculty of Business and Economics, University of Basel, Basel, Switzerland. It was published online on January 20 in JAMA Network Open.

LIMITATIONS:

According to the authors, potential limitations include exposure misclassification due to multiple water districts serving residents in a county, though sensitivity analyses with counties having more than 90% fluoridation coverage showed similar results. The researchers also noted that water districts may have implemented other treatment technologies concurrent with CWF, though the likelihood of these changes precisely offsetting any CWF effects was considered low.

DISCLOSURES:

The study received support from Ambizione grant PZOOP1_223786 from the Swiss National Science Foundation and Paul B. Beeson Emerging Leaders Career Development Award in Aging K76AG095036 from the National Institute on Aging. Lisa Simon, MD, DMD, disclosed receiving grants from the National Institute of Dental and Craniofacial Research and CareQuest Foundation, and personal fees from the California Dental Association, Santa Fe Group, American Dental Association, and Society of Teachers of Family Medicine outside the submitted work.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.