An enlarged hard stomach after a transplant pregnancy is not normal and is mostly caused by ovarian hyperstimulation syndrome. In most cases, the body overreacts to the ovulation stimulating drugs after transplantation, which leads to an increase in blood vessel permeability due to the enlargement of the ovaries bilaterally, and blood accumulates in the interstitial spaces of the tissues through the walls of the blood vessels, which leads to a decrease in blood volume and concentration of blood, resulting in the symptom of fluid retention in the thoracic and abdominal cavities. As a result, the stomach will become large and hard after the transplantation of pregnancy. Some women may experience nausea and vomiting, and if severe, it may lead to liver and kidney function damage, so it is recommended to go to the hospital in time to do relevant examinations. After the transplant, women should follow the doctor’s instructions and go to the hospital for regular checkups to understand the situation after the transplant, and inform the doctor in time if there is any abnormality.