Under normal circumstances, a woman produces one egg per month. For IVF pregnancy, multiple eggs are retrieved for fertilization. Before entering the menstrual cycle for egg retrieval, the doctor will first administer ovulation stimulating medication. Generally, egg retrieval can be performed when the number of mature follicles in the ovaries reaches 3-5, around the 10th-12th day of menstruation, and the follicles are about 12-14mm in diameter. The symptoms of lower abdominal pain after egg retrieval should be observed for ovarian hyperstimulation syndrome, which causes ovarian enlargement, abdominal distention, large amount of abdominal fluid and blood concentration leading to serious complications, and should be treated clinically and promptly. After egg retrieval, it is important to pay attention to the observation of the urine volume, because after hemoconcentration, the urine volume will decrease, which can lead to damage of important organ functions and must be treated promptly.