Early pregnancy is part of the eugenics process, and there are some embryos that are not well developed or fetuses that are particularly unstable and prone to spontaneous abortion. The symptoms of spontaneous abortion are mainly the following: 1. vaginal bleeding. If abnormal bleeding occurs in early pregnancy, the possibility of miscarriage should be considered. 2. abdominal pain. If the abdominal pain is more obvious, there is also a risk of miscarriage. 3. very low progesterone and a bad doubling of HCG, both of which represent the viability of the embryo. 4. when checking the ultrasound, it suggests that the position of the gestational sac is close to the cervical opening, while there may be more obvious bleeding.