Biochemical pregnancies usually bleed when they are about 30 days old, but there are individual variations. Biochemical pregnancy is a kind of hidden abortion, refers to the formation of fertilized eggs but failed to bed, caused by the blood HCG (human chorionic gonadotropin) levels rise transiently, before menstruation vaginal bleeding occurs in abortion, so biochemical pregnancy is usually around 30 days of pregnancy bleeding, and the amount of bleeding than the usual amount of menstruation is a little more than the amount of bleeding, lasts for about 7 to 10 days, no abdominal pain and other discomforts. There is no need to be overly nervous about the occasional occurrence of a biochemical pregnancy, and when the vaginal bleeding clears up, it will not affect another pregnancy. However, for recurrent biochemical pregnancy, we should carry out relevant examinations under the guidance of doctors, such as ultrasonography, endocrine examination, rheumatism and immunity, etc., to find out the causes and actively treat them before preparing for pregnancy.