Exposure of the Foetus Sample Clauses

Exposure of the Foetus. In a foetus, or unborn child, the number of cells is less than in the adult and the cells are rapidly dividing. As radiation damage is more extensive on dividing cells, the foetus is particularly sensitive to radiation damage and exposure to high doses could result in possible malformation or even death. For this reason and because it is possible that exposure to radiation at any time in pregnancy may increase the probability of cancer in the child, special radiation protection measures are necessary to protect the foetus Research on the biological effects of ionizing radiation on developing foetus has mainly concentrated on the Hiroshima and Nagasaki bomb victims as well as the Chernobyl accident in 1986. These studies have indicated that exposure to radiation during the first two weeks of pregnancy has not resulted in deterministic or stochastic effects to the child. Moderate doses of radiation can produce catastrophic effects on the developing embryo and foetus. In determining the effects of radiation on a developing embryo or foetus, the principal factors of importance are the dose and the stage of gestation at which the dose is delivered. Dose rate is also a factor, since many pathologic effects on the embryo are reduced significantly by reducing the dose rate. Gestation in humans is divided into Preimplantation - 0 through 9 days Organogenesis - 10 days through 6 weeks foetal period - 6 weeks through term The principal effects of radiation on the developing embryo and foetus are:  growth retardation;  embryonic, neonatal, or foetal death;  congenital malformations;  functional impairment, such as mental retardation. The foetal thyroid, which starts to concentrate iodine at about the 12th week of pregnancy, can be damaged if it is exposed to iodine-131. Radioactive iodine-131 is widely used for treatment of hyperthyroidism and thyroid cancer. Typically, a therapeutic treatment results in a total- body dose of 50 to 150 mGy (5-15 rad) from the isotope circulating in the blood. Pregnancy is, of course, a contraindication to the treatment with iodine-131. Treatment should be delayed, if possible, to eliminate the potential effects during pregnancy. Additionally, one must consider that the foetal thyroid begins to function after ten to twelve weeks of pregnancy and that by the third trimester the foetal thyroid avidly takes up iodine. Important Remember to For these reasons, radionuclide therapy or scans using 131I must not be given to pregnant women....