What are the symptoms of ovarian hyperstimulation syndrome? Ovarian hyperstimulation syndrome, or OHSS, is a disorder that occurs after ovulation promotion, especially during in vitro fertilization (IVF) treatment, mostly during the luteal phase of the ovulation promotion cycle and early pregnancy. Patients may experience gastrointestinal symptoms after egg retrieval, such as abdominal distension, nausea, vomiting, diarrhea, etc. Abdominal distension gradually increases due to enlarged ovaries and increased ascites; chest tightness and breath-holding may occur due to large amount of ascites or pleural fluid, coughing may occur during pleural fluid, and respiratory distress in severe cases; due to increased abdominal distension, patients eat less and may experience oliguria, and even dizziness, headache and fainting. What is the incidence of OHSS? Who is the high-risk group? OHSS mostly occurs in young, thin patients with polycystic ovary syndrome (PCOS). The likelihood of OHSS is increased if there are too many follicles after ovulation, and further increased if the embryos are transferred and pregnancy occurs, so it is recommended that fresh cycles of frozen embryos are not transferred in this group of patients. There are also patients with few follicles who develop OHSS after pregnancy. What is the prevention and treatment of ovarian hyperstimulation syndrome? If there are many follicles after egg retrieval, fluid drip can be given to expand the volume and drink more water, especially diuretic foods such as winter melon soup and watermelon; patients with only mild abdominal distension can be left untreated, but they should not be strenuously active or bedridden for a long time; if the distension worsens, they can be followed up in the outpatient clinic. OHSS is a self-limiting disease that improves with the onset of menstruation in non-transplanted or non-pregnant patients; in pregnant patients, the disease persists for 2-3 weeks during early pregnancy.