Radiological investigation of female of reproductive age group is restricted to

B i.e. First ten days of M.C. Ten day Rule : Radiological investigation in a reproductive age gp. female should be carried out within 10 days of last Menstrual Period i.e. Ist 10 days of M.C. Q (i.e. within in 10 days of onset of menstruation). This was stated in the belief that there was then least likelihood of conception taking place (but if it did, the embryo would be most sensitive to radiation) it is now believed that fetus is relatively insensitive to radiation in early stages of pregnancy, any adverse effect leads to spontaneous aboion. The fetus is most sensitive to radiation, at 8-15 weeks gestation for increased incidence of Down's Syndrome and slight reduction in IQ.