Objective Despite widespread general population exposure to mercury (Hg), there is limited human data on potential reproductive health effects at environmental background levels. The objective was to determine the relation between hair Hg levels and early developmental endpoints in couples undergoing IVF. Design Prospective cohort study of couples presenting for infertility treatment at an academic hospital. Materials and methods In women undergoing IVF, the proximal 3-cm length of a hair sample was analyzed for total Hg content. The following endpoints for embryo quality and early developmental outcomes were collected: number oocytes retrieved, total number of mature oocytes, fertilization rate, and embryo grades (1-5, 1 being the best) on days 2, 3 and 5. Linear mixed effects regression models were used to explore the associations between these outcomes and hair Hg, accounting within-woman correlation of outcomes and controlling for maternal age. Results 22 women provided a hair sample with a mean (SD) hair Hg concentration of 2.1 parts per million (1.7), with a range 0.038 to 5.7 ppm. The median (25th, 75th %ile) was 1.6 ppm (0.5, 3.3). EPA reference dose is 1 ppm. Increased Hg levels were associated with decreased oocyte quantity, increased fertilization rate and decreased embryo quality, though none of the associations were statistically significant at the 0.05 level. Hg above 1 ppm was associated with a -3.025 (95% CI: -7.00, +0.95; P=0.16) change in number of oocytes retrieved and a -2.989 (95% CI: -6.45, +0.47; P=0.11) change in number of mature oocytes. Each 1 ppm increase in Hg was associated with an estimated 0.037 (95% CI: -0.02, 0.10; P=0.25) increase in fertilization rate. Each 1 ppm increase in Hg was associated with an estimated 0.070 (95% CI: -0.10, 0.24; P=0.43) increase in day 2 score, a 0.105 (-0.09, 0.30; P=0.29) increase in day 3 score, and a 0.215 (-0.06, 0.49; P=0.13) increase in day 5 score. Conclusions In this small patient sample, some women undergoing IVF had elevated hair Hg levels. We found some evidence of a relationship between hair Hg concentrations and oocyte quantity, and a trend of an association between hair Hg levels and poorer embryo quality. As this is an ongoing study, additional patients and IVF data will be included in future analyses.
Harvard School of Public Health, Department of Environmental Health, 677 Huntington Avenue, Boston, MA 02115
Harvard University, School of Public Health, Boston, Massachusetts