The most common neoplasms in pregnant women are: breast cancer, cancers of the reproductive organ (in particular cervical cancer) and gastrointestinal tract, lymphomas and melanoma. Both diagnosis and treatment of cancer in pregnancy encounter numerous obstacles and therefore they should be conducted by an interdisciplinary team of physicians. The primary aim should always be the protection of life and health of the mother and the lowest possible risk of adverse effects induced by the diagnosis and therapy to the fetus. A surgical procedure is one of the basic methods of oncological treatment, also in pregnant patients. However, its extent depends on the type of cancer, gestational age and fetal development. Radiotherapy of the pelvic and abdominal regions during pregnancy is absolutely contraindicated due to severe (also lethal) consequences to the fetus. Chemotherapy with selected drugs is allowed after organogenesis. The therapy should end approximately three weeks prior to the planned labor. The incidence of malignant ovarian cancers is approximately 1 per 10 000–38 000 pregnancies. In the majority of cases, pregnancy does not affect prognosis. The therapeutic management primarily depends on the clinical advancement of cancer. In early stages, surgical intervention should be limited to unilateral salpingo-oopheorectomy as well as biopsy of the peritoneum and greater omentum. Following the conclusion of pregnancy and postpartum period, a repeated surgery to assess the advancement of the disease should be considered. In advanced diseases, the extent of surgical treatment depends mainly on the patient’s decision to maintain the pregnancy.