The relationship of hair mercury levels with early in vitro fertilization (IVF) outcomes

Abstract

OBJECTIVE: Environmental mercury (Hg) contamination has led to increased human exposure through the primary route of seafood consumption. Despite widespread exposure, data is limited on the impact of Hg on reproduction. We conducted a preliminary study of the potential impact of Hg on early human reproduction. DESIGN: Prospective cohort study on the association of hair Hg in women and early IVF outcomes. MATERIALS AND METHODS: Total Hg in parts per million (ppm) was measured in the proximal 3-cm of hair in women prior to their IVF cycle. Outcomes included number of oocytes, fertilization rate, blastocyst development and implantation failure. Covariates included age, stimulation protocol, day 3 FSH, peak serum estradiol and Omega-3 fatty acid (FA) consumption through self-reporting in a food survey. Generalized estimating equations were used to explore the associations between outcomes and hair Hg levels, accounting for within-woman correlations of outcomes across repeated treatment cycle attempts. We applied the Poisson log link function for the early embryo and oocyte level outcomes. RESULTS: There were a total of 170 cycles from 120 women. The mean hair Hg level was 1.07 ppm (range 0.03 to 5.66 ppm), 33% of the women exceeded the EPA reference dose of 1 ppm. Number of oocytes (p for trend=0.23) and fertilization rate (p for trend=0.29) did not differ by Hg level quartiles. A one log unit increase in Hg was associated with a 25% increased incidence rate of blastocysts (p=0.002) and a 44% decreased odds of implantation failure (p=0.021). CONCLUSION: Unexpectedly there was a positive association of hair Hg levels with indicators of successful early IVF outcomes. Since fish consumption may be beneficial for reproductive success and it is the primary source of Hg exposure, it may confound the association of Hg with IVF outcomes.