Effect of ionizing radiation on the female reproductive system.

The tendency towards postponement of maternity implies a greater exposure of female germ cells to damaging environmental effects, including ionizing radiation (IR). Progress in paediatric oncology, based on the use of radiotherapy, also implies the occurrence of gonadal dysfunctions and subsequent female fertility disorders. Therefore, it seems justifiable to systematize the state of knowledge concerning the effect of IR on the female reproductive system. A considerable part of studies concerning the effect of IR on female germ cells have been conducted on animals. Their extrapolation to humans is hindered because in animal studies high acute exposures are applied, which do not reflect human environmental exposures characterized by chronic low dose exposure. Studies on animals provide a heterogenous image, which hinders the formulation of unequivocal conclusions and indicates that radiosensitivity depends, i.a. on IR dose, stage of development of oocytes, the applied marker of the effects of IR, or on the species. LD50 of human oocytes is estimated to be below 2 Gy. The effect of IR depends, i.a. on the dose fractionation and the age (older women are more radiosensitive). In females, the effective sterilizing dose is: at birth 20.3 Gy, at 10 years 18.4 Gy, at 20 years 16.5 Gy, whereas at 30 years 14.3 Gy, which is associated with the available pool of ovarian follicles. Within the range of low doses received as a result of environmental exposure to IR, there is no evidence for the occurrence of either adverse pregnancy outcomes, nor fertility disorders in females. These effects may be related to the cancer radiotherapy, or exposure to high IR doses during nuclear accidents.