Iranian Journal of Nursing and Midwifery Research1735-906624420190703310312ENDepartment of Obstetrics and Gynecology, Mashhad University of Medical Sciences, Mashad, IranDepartment of Obstetrics and Gynecology, Neonatal and Maternal Research Center, Mashhad University of Medical Sciences, Mashhad, IranDepartment of Community Medicine and Public Health, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran2019070320190703Most cases of Ovarian Hyperstimulation Syndrome (OHSS) are associated with the use of exogenous gonadotropins for the induction of multiple oocytes. However, OHSS is rarely associated with a spontaneous ovulatory cycle in women with multiple gestations, hypothyroidism, polycystic ovary syndrome, or molar pregnancies. Herein, we report a case of OHSS in a woman with spontaneous pregnancy, without any underlying diseases or risk factors. The clinical findings showed abdominal pain, nausea, dyspnea, and amenorrhea. After imaging and laboratory tests, the final diagnosis was established. The patient was managed successfully without any complications. In conclusion, although spontaneous ovarian hyperstimulation is a rare condition, physicians should be able to diagnose this condition. In fact, early diagnosis and successful management can potentially prevent serious complications, which are likely to develop rapidly in patientshttp://ijnmr.mui.ac.ir/index.php/ijnmr/article/view/1644http://ijnmr.mui.ac.ir/index.php/ijnmr/article/download/1644/70707199