[Effects of ionizing radiation on the embryo and fetus]

The developing embryo and fetus are extremely sensitive to ionizing radiation. The main effects of radiation on he human embryo and fetus are: growth retardation, prenatal or neonatal death, congenital malformations and mental retardation. The incidence of these radiation effects at different stages of gestation, the relations with absorbed doses and threshold doses are discussed. Epidemiological data that reveal high susceptibility to carcinogenic effects of radiation during in utero life are presented. A dose of 0.1 Gy (10 rad) to the embryo and fetus is recommended as a threshold dose, above which a therapeutic abortion should be considered. Diagnostic radiation exposures will reach this level in a very rare cases. The threshold dose, which is an indication for pregnancy termination must be flexible, in a large tolerance, depending on other possible risks of the pregnancy as well as the personality of the future parents.