The lower edge of the gestational sac is best examined by ultrasound if it is greater than 20mm from the scar. If the lower border is less than 10 mm or even closer to the scar, there is a clinical risk of pregnancy at the scar with further growth and development of the gestational sac. This can lead to serious consequences, such as localized rupture, massive bleeding and endangering the life of the pregnant woman, and once there is massive bleeding the fetus is often unstable and can lead to intrauterine death. Therefore, if the lower edge of the gestational sac is less than 10 mm or closer to the scar incision, it is recommended to closely observe the pregnancy and terminate it under hysteroscopy if necessary.