Abstract
The evidence relating to pre-natal radiation exposure and the subsequent occurrence of malformations and cancer suggests that the overall risk lies in the range 0-1 cases/1000 irradiated by 1 rad in utero in the first 4 mo. of pregnancy. The natural level of occurrence of serious handicaps in average pregnancies is at least 30 times higher. The much lower probability of radiation-induced harm may not be sufficiently high to justify concern when a woman who was irradiated is discovered to be pregnant or the maintenance of restrictions on medical uses of ionizing radiation in women in the reproductive age, such as the 10 day rule?