A 28-year-old woman sought medical advice in the gynecology department because of infertility. Based on the results of the infertility workup, it was decided to apply in vitro fertilization treatment in her case. On the 12th day after embryo transfer, the patient was admitted to hospital because of nausea, vomiting, abdominal distention, and difficulties in breathing. The diagnosis was early pregnancy and the ovarian hyperstimulation syndrome (OHSS). After conservative treatment, the OHSS symptoms disappeared, and she was discharged in a good condition. However, nine days later the patient was readmitted due to a dull pain in her left shoulder, radiating onto the neck and left arm. Ultrasound examination revealed a thrombotic clot at the junction of the left external jugular vein and subclavian vein. Treatment with low-molecular-weight heparin was initiated. After 21 days of medication, the patient's symptoms resolved and, further, her pregnancy continued without complications. Although thromboembolic events are not frequently encountered in the course of OHSS, prophylactic anticoagulant therapy should be considered in all such patients.