The occurrence of malignancies during pregnancy has increased over the last decades. They complicate approximately 1 per 1000 pregnancies. The most common malignancies associated with pregnancy include malignant melanoma, malignant lymphomas and leukemia, and cancer of the cervix, breast, ovary, colon and thyroid. Since it is impossible for prospective randomized clinical trials to be conducted in this field, relevant data have been generated from case reports and matched historical cohort studies in order to evaluate the treatment outcomes and the issues complicating the management of malignancy in the pregnant patient. There is almost always a conflict between optimal maternal therapy and fetal well-being. The maternal interest is for an immediate treatment of the recently diagnosed tumor. However, the optimal therapy, be it chemotherapy, radiotherapy or surgery, may impose great risks on the fetus. Consequently, either maternal or fetal health, or both, will be compromised. Therefore, both the pregnant patient and her physician are often in a dilemma as to the optimal course. On the basis of the medical facts, we discuss the issues raising potential ethical conflicts and present a practical ethical approach which may help to increase clarity in maternal-fetal conflicts. We review the available data informing the incidence and impact of the most common malignancies during pregnancy and their treatment on both the pregnant woman and her fetus. The optimal therapy for the tragic diagnosis of cancer in pregnancy requires a collaborative and interdisciplinary approach between gynecologists, oncologists, obstetricians, surgeons, neonatologists, psychologists, nursing staff and other disciplines. The purpose of this article is not to answer specific questions or to construct management schemes for specific tumors but to provide a framework for approaching some of these complex issues.Keywords Cancer in pregnancy AE Maternal-fetal conflict AE Patient autonomy AE Maternal beneficence AE Fetal beneficence Conflicts raised by issues complicating the management of ''cancer in pregnancy'' Any choice of the best possible treatment option for pregnant women with cancer has to be based on precise medical facts. However, there are-arising from the special constellation of concomitant cancer and pregnancy-a number of issues seriously complicating the management of malignancy in the pregnant patient. Severe conflicts arise concerning the health and life of the mother and fetus by the diagnosed tumor and its therapy. One major conflict is the question: Should the therapy of choice be different in the presence of a pregnancy? The presence of a pregnancy aggravates the situation for the physician and the patient because the decision made needs to take into account the interests of the mother and the fetus. Possible conflicts are raised by different issues which complicate the management of cancer in the pregnant woman in a distinctive manner different to tumor therapy outside pregnancy. The complicating issues relate to (1) medical...