Prenatal fluoride exposure and motor development among infants in Los Angeles, California.

BACKGROUND

Prenatal fluoride exposure, at United States (US) population relevant levels, has been associated with poorer child neurodevelopmental outcomes; however, no US study has examined whether these associations manifest in infancy. This study investigated associations between prenatal fluoride exposure and infants' neurodevelopment in Los Angeles, California.

METHODS

Participants were from the Maternal and Developmental Risks from Environmental and Social Stressors (MADRES) cohort. MADRES is a predominately Hispanic prospective pregnancy and birth cohort in urban Los Angeles. Third trimester specific gravity-adjusted maternal urinary fluoride (MUFSG) concentration was a biomarker of fluoride exposure. Infant motor development, problem solving, communication and personal-social functioning at 6, 9, 12, and 18-months were assessed with the Ages and Stages Questionnaire-3 (ASQ-3). ASQ-3 scores were reverse coded, such that higher scores indicate worse performance. Longitudinal negative binomial regression examined associations between MUFSG and ASQ-3 scores adjusted for maternal age, race/ethnicity, income, BMI, infant sex and corrected infant age at ASQ-3 assessment.

RESULTS

Among 346 mother-child pairs, the median (IQR) MUFSG was 0.79 (0.54-1.07) mg/L. Higher MUFSG was associated with worse gross motor performance (IRR = 1.22, 95% CI: 1.03-1.45, p = 0.02). No significant associations were observed between MUFSG and fine motor: IRR = 1.15 (95% CI: 0.96-1.39), problem solving: IRR = 1.15 (95% CI: 0.90-1.48), personal-social: IRR = 1.04 (95% CI: 0.83-1.31), or communication: IRR = 0.90 (95% CI: 0.71-1.14) scores.

CONCLUSIONS

Third trimester fluoride exposure may increase risk of developmental neurotoxicity manifesting in infancy. Additional studies are needed to further explore this association across other US-based regions and the nation.