Biochemical pregnancy: It refers to a transient HCG elevation about 15 days after the menstrual period or the embryo transfer, followed by a menstrual flow. It is usually the result of sperm-egg union, which is usually secreted by chorionic gonadotropin seven days after sperm-egg union, and can be detected by early pregnancy test paper after another seven days, often indicating sperm-egg union and HCG secretion. “This is called biochemical pregnancy, or biochemical pregnancy miscarriage. Causes of biochemical pregnancy: The main causes are poorly developed embryos and abnormal chromosomes. This is more common in some women who are undergoing IVF. However, most women ignore it as a delayed menstruation because they did not go to the hospital for examination and they do not care about it, but in fact it is already a spontaneous miscarriage. Do not be alarmed if a woman of age encounters such a situation, as it is the result of natural elimination and usually does not affect the next pregnancy. If this happens repeatedly, it is time to go to the hospital for further examination.