RADIOTHERAPY DURING PREGNANCY - EFFECTS ON FETUSES AND NEONATES

To optimize the efficacy of radiotherapy for cancer patients who are p regnant, the following factors must be considered: the potential effec ts of the therapy on fetuses and neonates, the stage and prognosis of the mother's disease, and the possible risks to the patient of restric ting cancer treatment. Malformations and mental retardation are the mo st serious consequences of fetal exposure to radiation that are observ ed after birth. The sensitivity to radiation is high from 2 to 8 weeks after conception for malformations and from 8 to 25 weeks (particular ly up to week 15) for mental retardation; the risk of mental retardati on declines rapidly after the 25th week of gestation. When a pregnant patient requires radiation therapy, the physician should consider feta l sensitivity to radiation in light of gestational age and the expecte d dose of radiation and should then calculate the risk to the fetus ve rsus the benefits to the mother. The risk is negligible if fetal expos ure does not exceed 0.1 Gy, preferably remaining below 0.05 Gy, during gestation. Furthermore, it is safest to administer radiotherapy durin g or after the 25th week of gestation.