The case of a 21-year-old patient is presented who was diagnosed simultaneously with myelodysplastic syndrome (MDS) in the form of refractory anemia and hormonal disturbances consistent with polycystic ovary syndrome (PCOS). The patient became pregnant 28 months after megachemotherapy and alloHSCT and delivered a healthy son. The patient's fertility was jeopardized due to both hormonal disturbances and megachemotherapy with cyclophosphamide and allogeneic transplantation; however, her age and body mass reduction in the peritransplant period were beneficial factors. Despite an autologous reconstitution after megachemotherapy and alloHSCT, the malignant neoplastic clone was eliminated and 5 years after transplant the patient remains free from the symptoms of MDS. Two years after the delivery her hormonal findings, including testosterone level, are within the norm, but menstrual bleeding remains irregular and there was a relapse of obesity. To the authors' knowledge, this is the first known case of pregnancy in a patient suffering from MDS and PCOS after HSCT from a sibling donor.