Prenatal exposure to bisphenol A (BPA), an estrogenic compound, has been shown to alter postnatal development at an environmentally relevant exposure level. To elucidate these low dose effects of preimplatation exposure to BPA, two-cell mouse embryos were cultured with 1 nM BPA. More embryos exposed to 1 nM BPA than controls reached the blastocyst stage. When the blastocysts with or without BPA exposure were transferred to uterine horns of pseudopregnant recipient mice not treated with BPA, the number of pups per litter and body weight at birth did not differ. At weaning on postnatal day 21, however, pups treated with 1 nM BPA during the preimplantation period were significantly heavier than controls. These findings suggest that BPA may not only affect early embryonic development even at low, environmentally relevant doses, but also may exert late effects on postnatal development.