The chance of spontaneous miscarriage is 15%, with early miscarriage occurring before 12 weeks accounting for 75%. Women who have had one miscarriage should not be too burdened and generally do not need to undergo a comprehensive systematic examination. However, if spontaneous miscarriage occurs two or more times in a row, it is called recurrent spontaneous miscarriage, and then a comprehensive and systematic examination is needed to clarify the cause of miscarriage and to provide targeted treatment. The causes of recurrent spontaneous miscarriage are complex. It is generally believed that the causes of early spontaneous miscarriage occurring before 12 weeks of pregnancy are mostly chromosomal abnormalities, luteal insufficiency, immune factors, etc.; while the causes of late spontaneous miscarriage occurring between 12 and 28 weeks of pregnancy are mostly uterine malformations, relaxation of the endocervix, systemic diseases, etc. However, there are nearly half of recurrent spontaneous abortions for which the etiology is not yet clear. 1, genetic factors: chromosomal abnormalities are a common cause of recurrent spontaneous abortion. In early pregnancy spontaneous abortion, the incidence of karyotype abnormalities is as high as 50-60%. At present, there is no effective treatment for miscarriage caused by chromosomal abnormalities, and only prenatal genetic counseling and diagnosis can be performed to estimate the probability of recurrence of fetal chromosomal abnormalities. Carriers of autosomal balanced translocations and Robertsonian non-homozygous translocations can be pregnant, but prenatal diagnosis should be done to ensure a normal karyotype baby. Carriers of Robertson homozygous translocations should be advised to use contraception or to use donor normal gametes for in vitro fertilization or embryo transfer. Couples with normal chromosomes and abnormal chromosomes in the abortion products should avoid the influence of adverse environmental factors to prevent abnormal eggs or sperm. Endocrine factors: About 20%-25% of recurrent spontaneous miscarriages are caused by endocrine abnormalities, among which early miscarriages are commonly caused by luteal insufficiency, hyperprolactinemia, hypothyroidism, uncontrolled diabetes, etc. For pregnant women with luteal insufficiency in early pregnancy, exogenous progesterone such as progesterone and human chorionic gonadotropin can be applied under the guidance of doctors until placenta formation. In women with hypothyroidism and diabetes mellitus, the pregnancy should be controlled with relevant medications before deciding on the timing of pregnancy. Patients diagnosed with hyperprolactinemia should be treated with drugs such as bromocriptine under medical supervision. In clinical practice, a combination of western medicine and Chinese herbal medicine is often used to treat this type of patients, and the results are more satisfactory. Anatomical factors: Anatomical factors include congenital abnormal uterine development, such as infantile uterus, unicornuate uterus, bicornuate uterus, longitudinal/transverse uterine septum, uterine cavity adhesions, submucosal fibroids, polyps, cervical insufficiency and so on. Most miscarriages occur in the second trimester (structural defects of the uterus, abnormal tolerability, inadequate blood supply). In most cases of recurrent spontaneous abortion due to anatomical factors, targeted surgery is usually possible. Especially for those with simple cervical insufficiency, the timely choice to perform endocervical ligation is very effective. 4, infection factors: female reproductive tract infection of a variety of pathogens can lead to miscarriage, the common are mycoplasma, chlamydia, toxoplasma, gonococcus, listeria, herpes simplex virus, rubella virus, cytomegalovirus and protozoa. Most of these infections, which have no obvious symptoms, should be examined before pregnancy to prevent accidents. The most sensitive medications should be selected for different pathogens before pregnancy. This includes immune boosters, antiviral drugs and antibiotics, etc. 5. Immune factors: During normal pregnancy, many changes occur in maternal immune function so that various immune factors are organically coordinated to maintain pregnancy together. When there is an abnormality in one of the immune factors, the mother may have immune rejection of the embryo or fetus, resulting in spontaneous abortion. Women with maternal closed antibody deficiency may be treated with active immunization before pregnancy in due course. Other antibody-positive people need to apply Chinese and Western medicine treatment before considering pregnancy. 6, male factors: this factor is often ignored in the past, in fact, semen factors, high sperm malformation rate, low sperm vitality, and other male factors can cause miscarriage. Once the occurrence of this type of disease, should do this aspect of the examination, do not put the blame on the wife. 7, other factors: serious systemic diseases, smoking and alcohol abuse and other bad habits, traumatic stimulation and adverse environmental factors can lead to miscarriage. In addition, 40% of recurrent spontaneous miscarriages cannot be detected by the current medical means. Recurrent miscarriage brings a heavy psychological burden to pregnant women and their families, but even if recurrent spontaneous miscarriage occurs, it should not be overly worried. Because recurrent spontaneous miscarriage is not an incurable disease, even without any treatment, there is a possibility of normal delivery. After a spontaneous miscarriage, the chances of having a normal delivery after another pregnancy is about 75%, after 2 times about 73% and after 3 times about 68%. Even if there are 4 consecutive spontaneous abortions, the chance of normal delivery in a second pregnancy is 55%. Therefore, patients with recurrent spontaneous abortion should actively cooperate with their doctors to find the cause of miscarriage. Under the guidance of the doctor, the patient can safely pass the pregnancy and deliver a healthy and lovely baby.