Maternal fluoride exposure linked to lower IQ in offspring

  • Green R & al.
  • JAMA Pediatr
  • 19 Aug 2019

  • International Clinical Digest
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  • Children whose mothers had higher fluoride exposure during pregnancy had lower IQs at the age of 3-4 years.

Why this matters

  • Community water has historically been fluoridated to prevent tooth decay.

Key results

  • Relative to peers living in areas with nonfluoridated tap water, women living in areas with fluoridated tap water had higher mean:
    • Urinary fluoride levels (0.69 vs 0.40 mg/L; P=.001).
    • Self-reported fluoride intakes (0.93 vs 0.30 mg daily; P<.001>
  • Urinary fluoride levels had differential effect by sex (P for interaction=.02), whereby each 1-mg/L increment:
    • Associated with lower IQ score in boys (B=–4.49; P=.02).
    • Not associated with IQ score in girls (B=2.43; P=.33).
  • Each 1-mg increment in maternal daily fluoride intake was associated with lower IQ score in cohort overall (B=–3.66; P=.04); no interaction by sex.

Expert comment

  • In an editorial, David C. Bellinger, PhD, MSc, writes, “The findings of Green et al. and others indicate that a dispassionate and tempered discussion of fluoride’s potential neurotoxicity is warranted, including consideration of what additional research is needed to reach more definitive conclusions about the implications, if any, for public health.”
  • In an Editor’s Note, Dimitri A. Christakis, MD, MPH, writes, “This study is neither the first, nor will it be the last, to test the association between prenatal fluoride exposure and cognitive development. We hope that purveyors and consumers of these findings are mindful of that as the implications of this study are debated in the public arena.”

Study design

  • Canadian prospective multicentre birth cohort study of 601 children born during 2008-2012 (41% lived in communities with fluoridated municipal water).
  • Main outcomes: IQ on Wechsler Primary and Preschool Scale of Intelligence-III.
  • Funding: National Institute of Environmental Health Science.


  • No control for behaviours affecting urinary fluoride levels.
  • Maternal urinary levels may not correlate well with foetal exposure.
  • Unmeasured residual confounding.