Can radiotherapy cause birth defects?

Sometimes: Significant radiation to a fetus between 8 and 18 weeks causes brain damage and mental retardation. Pregnant women should delay radiation therapy when possible until after the baby is born. However, radiation therapy can be used in pregnant women with shields that protect the fetus if the area radiated is far enough away. Radiation in non-pregnant women or men does not cause birth defects.

Yes: There is a possibility that if the ova or sperm are exposed to radiation then genetic changes can occur. Patients are told to wait 6 months before getting pregnant.