There are many causes of miscarriage and the incidence is increasing. From the perspective of natural selection, sometimes miscarriage is a good thing to avoid the birth of abnormal fetuses, but multiple miscarriages will cause a great psychological shadow. Therefore, patients with a history of miscarriage should be examined before having another baby. The causes of miscarriage are too numerous to cover all of them, and the common causes are summarized as follows: I. Embryonic factors Embryonic chromosomal abnormalities are the most common, including quantitative and structural abnormalities. Quantitative abnormalities include: (1) chromosome trisomy (chromosomes 13, 16, 18, 21, 22); (2) 45, X haploid; (3) chromosome triploidy, tetraploidy; chromosome structural abnormalities include chromosome deletion, inversion, duplication. Embryonic chromosome abnormalities are examined by retaining embryonic tissues and then performing chromosome examination. Second, maternal factors 1, couple chromosomal abnormalities: can be detected by blood sampling, if there is indeed an abnormality, some patients can be reproduced through in vitro assisted reproduction. 2, genital malformation: unicornuate uterus, bicornuate uterus, double uterus, longitudinal uterus; uterine adhesions caused by scraping, infection, placental residue, etc.; cervical insufficiency; uterine tumor, etc. 3, reproductive tract infection: mycoplasma, chlamydia, toxoplasma, tuberculosis and other bacteria, viruses, atypical microorganisms. 4, immune factors: antiphospholipid antibodies, closed antibodies, etc. 5.Thrombotic state: blood hypercoagulation. 6.Endocrine factors: polycystic ovary syndrome, hyperprolactinemia, diabetes mellitus, abnormal thyroid function, luteal insufficiency, etc. 7.Other medical and surgical diseases: hypertension, kidney disease, tuberculosis, tumor, fever, anemia, heart disease. 8, radioactivity, dust, chemical substances, smoking and drinking, mental stress, psychological factors. The causes of miscarriage are complex and generally need to be ruled out item by item, so there are more examination items, each hospital has different examination items according to their own conditions, and professional reproductive specialists will generally carry out systematic examination.