Influence of oral and subcutaneous bisphenol-A on intrauterine implantation of fertilized ova in inseminated female mice.

Intrauterine implantation of fertilized ova in inseminated females is sensitive to minute levels of natural estrogens. Bisphenol-A (BPA), a widely used chemical in the production of polycarbonate plastics and epoxy resins, can be estrogenic. Here we administered BPA during the period of implantation to determine levels of exposure required to terminate pregnancy in mice. Varied doses were given through either injection or ingestion. Subcutaneous injections during days 1-4 of gestation significantly reduced litter size at 3.375 mg/day and substantially reduced the proportion of females that were parturient at 10.125 mg/day. Uterine implantation sites were also significantly reduced in females sacrificed at day 6 after receiving 10.125 mg/day. Exposure to lower doses was without significant effect. When inseminated females' diets were supplemented on days 1-5 with peanut butter contaminated by 0.11-9.0% BPA, litter size and percent parturient were not affected. However, when the animals' diet was exclusively comprised of a mixture of BPA, peanut butter, and powdered chow during days 1-4, an average daily intake of 68.84 mg BPA terminated all pregnancies. No significant effects at lower doses of BPA were seen in number of births or other measures through either mode of administration.