The frequency of malignant neoplasms during pregnancy has recently become a usually problem in modern medical practice. On average, 1 in 1,000 women will experience cancer during pregnancy. The most common pregnancy-related cancers include cervical, breast, ovarian, malignant melanoma, malignant lymphomas and leukemia, as well as colon and thyroid cancers. The main factor of late diagnosis and poor treatment results is the non-specificity of the symptoms of the disease in the early stages. The occurrence of difficulty at the diagnostic stage is an underestimation of the indications for conducting a diagnostic search. Signet ring cell carcinoma of the stomach is characterized by an aggressive course, rapid metastasis, and therefore is more often diagnosed in late stages and is a prognostically negative histological variant of stomach cancer. Stomach cancer during pregnancy is estimated to complicate 0.026–0.1 % of all pregnancies In this clinical case, an example of the course of signet ring cell carcinoma of the stomach against the background of pregnancy with dichoric diamniotic twins with increasing protein-energy deficiency is given.