Abstract

Excerpt:

2.1. Participants

Pregnant women were enrolled in the Maternal-Infant Research on Environmental Chemicals (MIREC) Study (Arbuckle, 2013) between 2008 and 2011 from ten cities across Canada, seven of which add fluoride to drinking water (Toronto, Hamilton, Ottawa, Sudbury, Halifax, Edmonton, Winnipeg) and three of which do not (Vancouver, Montreal, Kingston). Women were eligible to participate if they were ? 18 years of age, able to communicate in English or French, and < 14 weeks’ gestation. Participants were considered ineligible if they had known fetal abnormalities, medical complications, or reported drug use. Of 2001 women recruited, 1983 consented to participate. Of these, 1885 (95.1 %) provided plasma samples in trimester one. We excluded those missing data on fetal sex (n = 9), for a final study sample of 1876 pregnant women.

The current study received approval from the research ethics boards at Health Canada and York University. All participants provided written informed consent at time of enrollment in MIREC.

4.2. Conclusions

In this Canadian pregnancy cohort, higher levels of fluoride exposure were associated with alterations in maternal thyroid hormone levels, the magnitude of which varied by fetal sex. Our findings make an important contribution to the growing body of evidence suggesting that higher levels of fluoride exposure in pregnancy may have adverse effects on maternal thyroid function. The implications of this work are of public health significance when considering the vital role of the maternal thyroid in supporting optimal fetal growth and neurodevelopment. Future studies in this area are warranted to replicate the current findings.

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