Recurrent spontaneous abortion (RSA) is a common condition among women of childbearing age who suffer 2 or more consecutive fetal losses (weight ≤500g) before 20 weeks of gestation with the same sexual partner. 2 or more abortions account for about 5% of women of childbearing age, while 3 or more abortions account for about 1% to 2%. 3 or more abortions before 28 weeks of gestation are called habitual abortions. After 2 spontaneous abortions, the risk of recurrence of miscarriage is about 3 times higher than that of the first, with an incidence of 38%; those with a history of 4 or more miscarriages, if not treated appropriately, most pregnancies are aborted again. The etiology of RSA is complex and the diagnosis of immune miscarriage, especially the diagnosis of the homozygous immune phenotype, relies mainly on the exclusion method. The main causes of recurrent miscarriage in patients are: anatomical factors; endocrine factors; immune factors; chromosomal factors; and infectious factors. Besides, there are still a few with unknown etiology, which are called recurrent miscarriage of unknown origin. 1.Uterine anatomical abnormalities Uterine anatomical abnormalities lead to recurrent miscarriage accounting for about 12%-15%, including various congenital malformations of the uterus, uterine adhesions, uterine fibroids or adenomyosis, and cervical insufficiency and other diseases. 2.Endocrine abnormalities Recurrent miscarriage due to endocrine abnormalities accounts for 12%-15%, mainly gynecological endocrine abnormalities, such as luteal insufficiency, polycystic ovary syndrome (PCOS), lactogen disorders, etc. Serious endocrine disorders can also lead to miscarriage, such as diabetes mellitus, hyperthyroidism or hypothyroidism. Therefore, patients with recurrent miscarriage should be careful to exclude when looking for the cause. Among the recurrent miscarriages caused by various reasons, the treatment of recurrent miscarriages caused by endocrine reasons is the best, and it has been reported that after the endocrine abnormalities are corrected, the success rate can be as high as 90% or more. 3.Immune recurrent miscarriage Recent studies on reproductive immunity have shown that about 50% to 60% of the causes of recurrent miscarriage are related to immune disorders. Different factors lead to different immunopathological changes in miscarriage. 4, the genetic factors of recurrent spontaneous abortion chromosomal abnormalities are a common cause of recurrent spontaneous abortion. In early pregnancy spontaneous abortion, the incidence of karyotype abnormalities is as high as 50% to 60%. About 3% to 8% of RSA couples have chromosomal abnormalities. 5, recurrent spontaneous abortion of infection factors female reproductive tract infection of a variety of pathogens can cause spontaneous abortion, common mycoplasma, chlamydia, toxoplasma, gonococcus, herpes simplex virus, rubella virus, cytomegalovirus, etc.. Most of these pathogens are subclinical or latent infections that may not show clinical symptoms, and patients with RSA should be tested for TORCH or have pathogens isolated and cultured before they become pregnant again to rule out the appropriate causative factors or for treatment.