Maternal urinary fluoride during pregnancy and birth weight and length: Results from ELEMENT cohort study

Impact of Fluoride Exposure on Rat Placenta: Foetal/Placental Morphometric Alterations and Decreased Placental Vascular Density

Inorganic fluoride is a geogenic and anthropogenic contaminant widely distributed in the environment and commonly identified in contaminated groundwater. There is limited information on the effect of fluoride exposure on pregnancy. The aim of this study was to evaluate possible placental alterations of fluoride exposure in a rat model simulating preconception and pregnancy exposure conditions in endemic areas. Fluoride exposure was administered orally to foetuses of dams exposed to 2.5 and 5 mg fluoride/kg/d. Foetal weight, height, foetal/placental weight ratio, placental zone thickness, levels of malondialdehyde (MDA) and vascular endothelial growth factor-A (VEGF-A) and vascular density in placental tissue were evaluated. The results showed a nonlinear relationship between these outcomes and the dose of fluoride exposure. In addition, a significant increase in the fluoride concentration in placental tissue was observed. The group that was exposed to 2.5 mg fluoride/kg/d had a greater increase in both MDA levels and VEGF-A levels than the higher dose group. A significant increase in the thickness of the placental zones and a decrease in the vascular density of the labyrinth zone area were also observed in the fluoride-exposed groups. In conclusion, the data obtained demonstrate that fluoride exposure results in morpho-structural alterations in the placenta and that non-monotonic changes in MDA, VEGF-A levels and placental foetal weight ratio were at environmentally relevant concentrations.

Water Fluoridation and Birth Outcomes in California

BACKGROUND

There is a lack of research on the relationship between water fluoridation and pregnancy outcomes.

OBJECTIVES

We assessed whether hypothetical interventions to reduce fluoride levels would improve birth outcomes in California.

METHODS

We linked California birth records from 2000 to 2018 to annual average fluoride levels by community water system. Fluoride levels were collected from consumer confidence reports using publicly available data and public record requests. We estimated the effects of a hypothetical intervention reducing water fluoride levels to 0.7  ppm (the current level recommended by the US Department of Health and Human Services) and 0.5  ppm (below the current recommendation) on birth weight, birth-weight-for-gestational age z-scores, gestational age, preterm birth, small-for-gestational age, large-for-gestational age, and macrosomia using linear regression with natural cubic splines and G-computation. Inference was calculated using a clustered bootstrap with Wald-type confidence intervals. We evaluated race/ethnicity, health insurance type, fetal sex, and arsenic levels as potential effect modifiers.

RESULTS

Fluoride levels ranged from 0 to 2.5  ppm , with a median of 0.51  ppm . There was a small negative association on birth weight with the hypothetical intervention to reduce fluoride levels to 0.7  ppm [- 2.2 g ; 95% confidence interval (CI): - 4.4 , 0.0] and to 0.5  ppm (- 5.8 g ; 95% CI: - 10.0 , - 1.6 ). There were small negative associations with birth-weight-for-gestational-age z-scores for both hypothetical interventions (0.7  ppm : - 0.004 ; 95% CI: - 0.007 , 0.000 and 0.5  ppm : - 0.006 ; 95% CI: - 0.013 , 0.000). We also observed small negative associations for risk of large-for-gestational age for both the hypothetical interventions to 0.7  ppm [risk difference  ( RD ) = - 0.001 ; 95% CI: - 0.002 , 0.000 and 0.5  ppm (- 0.001 ; 95% CI: - 0.003 , 0.000)]. We did not observe any associations with preterm birth or with being small for gestational age for either hypothetical intervention. We did not observe any associations with risk of preterm birth or small-for-gestational age for either hypothetical intervention.

CONCLUSION

We estimated that a reduction in water fluoride levels would modestly decrease birth weight and birth-weight-for-gestational-age z-scores in California. https://doi.org/10.1289/EHP13732.

Association between Water Fluoride Levels and Low Birth Weight: National Health and Nutrition Examination Survey (NHANES) 2013-2016

Background: Excessive fluoride consumption affects reproductive and child health. We examined the association between levels of fluoride in drinking water and birth weight, in the National Health and Nutrition Examination Survey 2013−2016, after adjusting for known risk factors Low Birth Weight (LBW) including age, smoking, and socio-demographic variables including education, food security, health care access, and health status. Methods: The study included 7147 and 6858 women with complete birth weight and water fluoride data, respectively. Linear regression models evaluated the association between water fluoride and birth weight across racial/ethnic groups. The odds of delivering an LBW infant (<2500 g) compared to an infant weighing ≥ 2500 g, as well as the odds of delivering a Very Low Birth Weight (VLBW, <1500 g) infant compared to an LBW infant were explored in separate logistic regression models. Results: Women with LBW infants were exposed to significantly higher levels of water fluoride compared to those with normal birth weight infants. Our findings suggest a significant association between excess water fluoride exposure (>0.7 ppm) and LBW weight in Hispanic women, independent of established LBW risk factors. In logistic regression models, Hispanic women exposed to increased levels of water fluoride were 1.5 times more likely to give birth to an LBW infant and 3.5 more likely to give birth to a VLBW infant. Conclusion: Taken together, these findings can inform public health education strategies that highlight water fluoride as a potential risk factor during pregnancy in Hispanic women. More research is needed to confirm these findings.