Three consecutive biochemical pregnancies may be caused by environmental factors, embryonic factors, bad habits, immune factors and so on. 1. Environmental factors: If men and women are exposed to excessive toxic substances in their lives, such as lead, formaldehyde and other chemicals, X-rays and other ionizing radiation, it will affect the quality of sperm and eggs, leading to the emergence of consecutive biochemical pregnancies. 2. Embryonic factors: embryonic chromosomal abnormalities are the most important cause of biochemical pregnancy, in which the number of abnormalities in trisomy is the most common, such as trisomy 16, 18, 21. Because of the poor quality of eggs and sperm, female endocrine abnormalities and other factors, affecting the quality of embryos and embryo implantation, so there will be three consecutive biochemical pregnancy. 3. Bad habits: such as smoking and alcohol abuse, drug abuse, excessive coffee drinking, often stay up late and other bad habits, can cause endocrine disorders in men and women, which in turn affects the quality of the embryo, resulting in three consecutive biochemical pregnancies. 4. Immune factors: women with autoimmune diseases, such as systemic lupus erythematosus, antiphospholipid syndrome, etc., will also have three consecutive biochemical pregnancies. If recurrent biochemical pregnancy occurs, the cause should be identified as soon as possible and appropriate treatment should be carried out according to the cause.