Effects of preimplantation treatment with aspirin and acetaminophen on blastocyst and fetus in rats

Pregnant rats were treated with ig aspirin (Asp) and acetaminophen (Ace) on d 3 of pregnancy (positive vaginal smear = d 0). Blastocysts were collected on d 4 and evaluated for gross morphology, cell number, micronucleus, and mitotic index. Some rats were killed on d 20 and fetuses were examined for teratogenic effects. On d 4 a reduction of cell number per blastocyst was found in the rats treated with Asp 0.5, 1 g.kg-1, and Ace 1 g.kg-1, while the mitotic index, frequency of micronuclei, and frequency of blastocysts with morphological alterations were increased. The frequency of micronuclei was increased in rats exposed to Ace 0.25 and 0.5 g.kg-1. On d 20 major malformation and embryotoxicity were seen in Asp 0.5, 1, and Ace 1 g.kg-1 groups.