Effects of bisphenol A (BPA) on placentation and survival of the neonates in mice

The effects of bisphenol A (BPA) on placentation have not been fully determined. The aim of this study was to clarify the structural changes of the placenta, abortion rate, and survival of neonates after BPA administration in mice. BPA (10 mg/kg/day) was administered to pregnant mice (BPA mice) subcutaneously from the first day of pregnancy (Day 0) to Day 7 (8 days total). The number of embryos and weights of whole uteri were measured on Days 10 and 12. Morphological changes in the placentae were examined by light microscopy on the corresponding days of pregnancy. The number of neonates was also counted. Survival rates were periodically calculated for neonates from the first day after parturition (P-Day 0) to P-Day 56. The number of embryos and weight of the uterus on Days 10 and 12 were significantly decreased by BPA injection. No notable differences were recognized between the left and right uteri. The proportion of the labyrinthine zone per whole placenta in the BPA mice became lower than that in the controls, and that of the metrial gland was higher in the BPA mice. The intervillous spaces of the placenta were narrower in the BPA mice. Degenerative changes were found in the trophoblastic giant cells and spongiotrophoblast layers of the BPA mice. The number of BPA mouse neonates was drastically decreased within 3 days after birth, and no mice survived after P-Day 56. The results suggest that BPA not only disrupts placental functions and leads to abortion through chronic stimulation of gene expression by binding to DNA but that it also affects the mortality of neonates through indirect exposure of embryos.