Ovarian hyperstimulation syndrome is caused by the body’s response to ovarian stimulating drugs such as clomiphene and is commonly seen in patients who use in vitro fertilization for assisted reproduction. In ovarian hyperstimulation syndrome, multiple follicles may be observed on ultrasound in both ovaries, and the enlarged ovaries may also show increased capillary permeability, causing abnormal extravasation of body fluids and proteins into the third interstitial space. These patients often develop abdominal distension, diarrhea, loss of appetite, nausea, vomiting, lower abdominal discomfort, heaviness or mild lower abdominal pain within 7 days after HCG injection. The diagnosis of ovarian hyperstimulation syndrome can be confirmed by ultrasound, and tests such as liver and kidney function, blood routine and water electrolyte measurement can indicate abnormalities.