Embryonic survival in mice exposed to X-rays during the preimplantation period.

The intrauterine development of embryos after exposure of mice to X-rays during the preimplantation period of gestation was investigated. Porton mice were whole-body-X-irradiated with a single dose of 500 R on the first, second, third or fourth day of the preimplantation period of pregnancy. Uterine contents were examined on the nineteenth day of gestation. As compared to non-irradiated control, in the uteri of irradiated female mice, a smaller number of live 19-day-old fetuses and a greater number of resorptions and non-implanted embryos were confirmed. Not all irradiated females had live 19-day-old fetuses in the uteri. Taking into consideration mice in whose uteri live fetuses were found, smaller mean numbers of 19-day-old fetuses in the uterus were calculated in irradiated females than in non-irradiated control. The adverse effects of X-irradiation in the preimplantation period depended upon the day on which the pregnant females were irradiated. These effects were most apparent in the case when the mice were irradiated on the first and third days of pregnancy, and less apparent after X-irradiation of females on the fourth and second days of gestation.