[Cancer and pregnancy: the medical oncologist's point of view].

Having to start chemotherapy during pregnancy remains a rare event. The decision to proceed with this treatment depends on the drugs used, the time of exposure for the fetus and the gestational age at the time of exposure. The mutagenic potential of the chosen drug has to be known. The risk for the child can then be established without compromising the mother's chances of survival or well-being. This type of situation generally arises in women with breast cancer, leukemia or lymphoma. The first trimester of pregnancy, which corresponds to organogenesis is the most critical period for the fetus. The greatest risk of malformation occurs with anti-metabolite drugs. Chemotherapy can also expose the child to direct in utero toxicity. Myelosuppression is the most common toxic effect, sometimes giving rise to infections and/or fetal hemorrhage. The long-term risks of cancer on the mother's subsequent fertility or the child's intellectual development are not well-known. Such factors must be examined in prospective studies and registered in a specific database.