Hi, Thanks for writing in. Leukemia in the mother can rarely be transmitted to progeny but more research is required. There is a gene known as the BCR-ABL fusion gene, or the Philadelphia chromosome which if present in the mother’s cancer cells can cross over to the baby. This is not fully understood. If the patient of leukemia is the father then the sperm DNA is not affected by the leukemia to cause the disease in next generation. However, as he might have got chemotherapy or radiation therapy at that time then it will help to get a semen analysis done to know if there is any condition like sub normal fertility due to cancer treatment. Fertility impairments among men treated during childhood for cancer are known to occur after some, but not all, types of anti-cancer therapy. Majority of survivors show no evidence of fertility impairment after cancer treatment of leukemia. However, men treated at a young age with high dose head radiation therapy may have impaired fertility.