Recent scientific data on prenatal effects of ionising radiation

Numerous studies were performed in our laboratory and in a few other laboratories, concerning the radiation susceptibility of pre-implantation and early post-implantation embryos. In contrast to an usual assumption, several studies suggested that, at least in some mouse strains, malformations can be induced by ionising radiation during the pre-implantation period, and that zygotes (= first day of pregnancy) are generally more at risk for such effects than later stages. In the Heiligenberger strain and the C57BL strain, irradiation of zygotes with doses higher than 0.5 Gy also revealed to be able to induce a genomic instability. In the Heiligenberger strain, the development of a genomic instability as well as the rate of malformations were transmitted to the next mouse generation after x-irradiation of zygotes with a high dose (1 Gy). Such transgenerational effects were not found in two other sensitive strains (ICR and CF1) after zygote x-irradiation with moderate doses (0.2 and 0.4 Gy). However, this treatment led to alterations of gene expression in the next generation embryos, the consequences of which are still undetermined. In agreement with others, our studies also showed that gene mutations may influence the sensitivity of early embryos to radiation induction of developmental effects.