[The problems raised by the irradiation of pregnant women. Effects of ionizing radiations on the embryon and foetus (author's transl)].

In man, the period of maximum risk for the embryo and foetus is between the second and tenth week after conception. The most frequent and most severe malformation is microcephaly which in extreme cases is accompanied by mental retardation. The results of studies in experimental animals and man agree that it is impossible to demonstrate any increased risk of malformation with doses below 15 rads, and that the increase over the spontaneous incidence of malformation is slight at doses below 25 rads. A very small increase in the frequency of leukaemias and cancers has been observed after irradiation in utero for pelvimetry, which delivers a few rads; it can be estimated from these data that a dose of 2 rads induces at the most the risk of one case of cancer in 2,000 children. In practice, it is only exceptionally that an abortion is advised after a diagnostic radiological examination, since the doses in these circumstances are relatively low. A therapeutic termination of pregnancy should be advised when the dose is greater than 20 rads, but it is necessary to take into account other medico-social factors. Conversely, it is important to avoid any irradiation in women who could be pregnant and in particular avoid any irradiation of the true pelvis during the 10 days prior to menses and especially if there has been a delay in the start of menstruation. In pregnant women radiological examinations should only be made if they are of paramount importance for the mother, and all precautions taken to reduce the dose to the uterus in the absolute minimum.