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JAMA Pediatr. 2019 Aug 19. doi: 10.1001/jamapediatrics.2019.1729. [Epub ahead of print]

Association Between Maternal Fluoride Exposure During Pregnancy and IQ Scores in Offspring in Canada.

Author information

1
Faculty of Health, York University, Toronto, Ontario, Canada.
2
Faculty of Health Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
3
Child and Family Research Institute, British Columbia Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada.
4
Pediatrics and Environmental Health, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio.
5
School of Dentistry, Indiana University, Indianapolis.
6
Department of Social and Preventive Medicine, Laval University, Québec City, Québec, Canada.
7
Centre de Recherche du CHU de Québec, Université Laval, Québec City, Québec, Canada.
8
School of Psychology, Laval University, Québec City, Québec, Canada.

Abstract

Importance:

The potential neurotoxicity associated with exposure to fluoride, which has generated controversy about community water fluoridation, remains unclear.

Objective:

To examine the association between fluoride exposure during pregnancy and IQ scores in a prospective birth cohort.

Design, Setting, and Participants:

This prospective, multicenter birth cohort study used information from the Maternal-Infant Research on Environmental Chemicals cohort. Children were born between 2008 and 2012; 41% lived in communities supplied with fluoridated municipal water. The study sample included 601 mother-child pairs recruited from 6 major cities in Canada; children were between ages 3 and 4 years at testing. Data were analyzed between March 2017 and January 2019.

Exposures:

Maternal urinary fluoride (MUFSG), adjusted for specific gravity and averaged across 3 trimesters available for 512 pregnant women, as well as self-reported maternal daily fluoride intake from water and beverage consumption available for 400 pregnant women.

Main Outcomes and Measures:

Children's IQ was assessed at ages 3 to 4 years using the Wechsler Primary and Preschool Scale of Intelligence-III. Multiple linear regression analyses were used to examine covariate-adjusted associations between each fluoride exposure measure and IQ score.

Results:

Of 512 mother-child pairs, the mean (SD) age for enrollment for mothers was 32.3 (5.1) years, 463 (90%) were white, and 264 children (52%) were female. Data on MUFSG concentrations, IQ scores, and complete covariates were available for 512 mother-child pairs; data on maternal fluoride intake and children's IQ were available for 400 of 601 mother-child pairs. Women living in areas with fluoridated tap water (n = 141) compared with nonfluoridated water (n = 228) had significantly higher mean (SD) MUFSG concentrations (0.69 [0.42] mg/L vs 0.40 [0.27] mg/L; P = .001; to convert to millimoles per liter, multiply by 0.05263) and fluoride intake levels (0.93 [0.43] vs 0.30 [0.26] mg of fluoride per day; P = .001). Children had mean (SD) Full Scale IQ scores of 107.16 (13.26), range 52-143, with girls showing significantly higher mean (SD) scores than boys: 109.56 (11.96) vs 104.61 (14.09); P = .001. There was a significant interaction (P = .02) between child sex and MUFSG (6.89; 95% CI, 0.96-12.82) indicating a differential association between boys and girls. A 1-mg/L increase in MUFSG was associated with a 4.49-point lower IQ score (95% CI, -8.38 to -0.60) in boys, but there was no statistically significant association with IQ scores in girls (B = 2.40; 95% CI, -2.53 to 7.33). A 1-mg higher daily intake of fluoride among pregnant women was associated with a 3.66 lower IQ score (95% CI, -7.16 to -0.14) in boys and girls.

Conclusions and Relevance:

In this study, maternal exposure to higher levels of fluoride during pregnancy was associated with lower IQ scores in children aged 3 to 4 years. These findings indicate the possible need to reduce fluoride intake during pregnancy.

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