The shape of the gestational sac is mainly round or oval. When the gestational sac has an irregular shape, is not full and wrinkled, and is located mainly in the lower part of the uterus, it is likely to be a sign of preterm miscarriage. At the same time, if the pregnancy is accompanied by abdominal pain and irregular vaginal bleeding, it is likely to cause a miscarriage. A small gestational sac is mainly caused by factors such as delayed menstruation and late conception. After pregnancy, the gestational sac will settle in the woman’s uterus, followed by the appearance of the fetal heart and fetal buds. It is important to go for regular check-ups already in the early stages of pregnancy and to preserve the fetus through reasonable means.