Introduction: OHSS is a rare complication occurs following the use of assisted reproductive technologies. Most of the current literature describes spontaneous OHSS in patients with endocrine disorders, pregnancy with triploidy & invasive mole etc. But we describe an interesting case of spontaneous OHSS with its management, which mimics as ovarian malignancy in some aspect with no risk factor to develop OHSS. Case report: A 25yr old G4P0120 at 9+3 weeks was referred to us with severe abdominal pain & distension for 1 day. On examination she had gross ascites with bilateral ovarian cyst of size 11×7 cm & 12×9 cm. Her CA 125, βhCG, Hb&Hct were 445U/ml, 212844.26 miu/ml, 15.5 g/dl & 48% respectively. Her ascitic fluid cytology and culture for tuberculosis were normal. She was managed conservatively for 2 days. But with deteriorating general condition decision for termination of pregnancy was taken. After that she has improved both clinically, radiologically and biochemically. Conclusion: Spontaneous OHSS is a rare condition. It should be diagnosed early. The main stay of management is conservative with proper vitals monitoring. In rare case sometime termination of pregnancy or surgical management is required to improve maternal condition.