Antenatal radiography and the ten-day rule

The assumption that the human fetus is not much more sensitive to the carcinogenic effects of low-level irradiation during early stages of development than during later stages was made by Dr. Mole (Lancet, 1976, i, 738). He calculated, on the basis of Oxford data, the cost in terms of childhood cancer induction of not taking any steps to avoid irradiation of pregnant women. An examination of the separate effects of four fetal irradiation subfactors (exposure age, number of exposures, reasons for the examinations and X-ray findings) has demonstrated that exposure age does exert an independent effect on the cancer induction risk, and for this effect first-trimester exposures are probably 16 times as dangerous as third-trimester exposures. It is emphasised that as a result of 10% of viable fetuses being involved in these examinations, there was between 1953 and 1970, a 5% addition to the number of children who died from malignant diseases. (U.K.)