The specific causes are as follows: a. Chromosomal abnormalities: refers to miscarriage caused by chromosomal abnormalities in both or one of the spouses or embryos. Common chromosomal abnormalities in couples are balanced translocation, Robertson translocation, etc. The most common chromosomal abnormalities in embryos are triploidy, followed by polyploidy, X haploidy, autosomal haploidy, balanced chromosomal translocation, deletion, chimerism, inversion, overlap, etc. Maternal reproductive tract anatomical abnormalities: 15%-20% of recurrent miscarriages are associated with uterine malformations, including unicornuate uterus, bicornuate uterus, double uterus and uterine longitudinal septum. In particular, incomplete longitudinal uterus is most likely to lead to recurrent miscarriage. Cervical insufficiency accounts for 8% of the causes of recurrent miscarriage and is likely to cause late miscarriage and preterm delivery. Submucosal fibroids and intermuscular fibroids larger than 125px are also related to recurrent miscarriage. Maternal endocrine disorders: luteal insufficiency, polycystic ovary syndrome, hyperprolactinemia and thyroid disorders, etc. Reproductive tract infection: about 0.5%-5% of recurrent miscarriages are related to infection. Mainly refers to the miscarriage caused by Toxoplasma gondii, cytomegalovirus, herpes simplex virus and other infections. V. Immune function abnormalities: 1. Autoimmune type: mainly refers to miscarriage caused by antiphospholipid antibodies, which belongs to the category of antiphospholipid antibody syndrome. The current antiphospholipid antibody detection indexes are: anti-cardiolipin antibody (ACL); anti-β2GP-l antibody; lupus anticoagulation factor (LAC). Positive diagnostic criteria are the presence of 2 or more positive antiphospholipid antibodies with an interval of 6 weeks or more. Positive indicators related to pre-thrombotic state. 2. Homozygous immune type: The diagnosis of this type of miscarriage is an exclusionary diagnosis, which means that chromosomal, anatomical, endocrine, infectious and autoimmune etiologies are excluded and other causes of miscarriage are not found. Sixth, thrombotic tendency: hereditary and acquired thrombotic tendency: such as genetic mutation, protein S and protein C deficiency leading to thrombotic tendency, homocysteinemia, etc. Corresponding auxiliary examinations: 1. Chromosome screening for both partners 2. Blood tests for female sex hormones, thyroid hormones and autoantibodies, blood glucose and insulin resistance 3. Anti-cardiolipin antibody, lupus anticoagulation factor, anti-β2 glycoprotein-1 antibody, anti-nuclear antibody, homocysteine, coagulation factor V mutation, protein S, protein C, platelet aggregation and D-dimer 4. Examination of ovarian reserve function and, if necessary, hysterosalpingography, hysteroscopy and ultrasonography. 5. Semen examination of the male partner