The hcg is a specific hormone secreted by gestational trophoblast cells. Usually the hcg reaches 100,000 or more, when embryonic abortion is less likely to occur. In the first trimester of pregnancy, the embryo is not stable because the placenta has not grown, and in the second trimester, it may be caused by poor quality of the embryo or various viral infections such as Toxoplasma gondii, herpes virus, cytomegalovirus, rubella virus, or even HPV virus, which usually occur in the second trimester. This usually occurs during the second trimester. After two months of pregnancy, the embryo may not be prone to sudden abortion because the embryo is growing relatively well and the placenta is slowly growing out. Most of the hcg above eight weeks of pregnancy can reach 100,000, so this is the time when embryonic stoppage is not easy to appear, but this is not absolutely will not occur. So women in the first trimester of pregnancy, as long as the placenta has not grown, then embryonic abortion may occur, at this time should try to pay attention to rest and avoid exposure to toxic and harmful substances, so as not to cause fetal abortion.