Effects of intrauterine radiation depen on the stage of pregnancy Irradiation durang 18th to 20th post conception day results in the expulsion cf the ovum The most critical period in foetal development is 20th to 50th post conception days Irradiation with 100-200 rads during this period results in major develop mental anomalies of C.N S, eyes and skeleton. After 50th day irradiation retards the foetal growth without any development defects Decision for radiation diagnostic and therapeutic use should be taken on its absolute and the relative necessity 618 2/ 3-006.3 04 Sarcoma.