Fetal arrest refers to the cessation of development or death of the embryo, 8 to 10 weeks of pregnancy during this period of time clinicians are prone to make a diagnosis of embryonic arrest, in fact, the embryo in any gestational week may be arrested, common causes are infection, genetics, immunity and other factors. 1. Infection: when the embryo is in the sensitive period of development and differentiation, it is easy to be affected by viruses, mycoplasma, toxoplasmosis and other malformations, resulting in abnormal embryonic development or cessation of development. 2. Genetic: abnormal chromosome number and structure will lead to normal cell differentiation can not be carried out, resulting in eventual miscarriage and embryonic arrest. 3. Immunity: If the mother and fetus do not have the same blood type, or if the mother has autoimmune disease, she may produce IgG antibodies that can damage the fetus through the placenta, which can also cause abnormal embryo development. In case of fetal arrest, you should go to the obstetrics and gynecology clinic in time to find out the cause and take appropriate treatment.