Spontaneous miscarriage is when the embryo stops developing before 28 weeks of gestation or is spontaneously expelled from the uterus. If spontaneous miscarriage occurs twice or more, it is called recurrent miscarriage; if it occurs three times or more, it is called habitual miscarriage. The incidence of spontaneous miscarriage is about 15%, recurrent miscarriage is about 5%, and habitual miscarriage is about 0.5%. Miscarriages that occur before 12 weeks of gestation are early miscarriages, while those that occur after 12 weeks of gestation are late miscarriages. The causes of spontaneous miscarriage are complex and include: anatomical abnormalities of the uterus, genetic factors, endocrine disorders, infections and so on. The rapid development of reproductive immunology in recent years has revealed that most recurrent miscarriages of unknown origin in the past were due to immune disorders. Recent clinical observations have also revealed that pre-thrombotic states can also lead to recurrent miscarriages. People who suffer from recurrent miscarriages are not only financially, physically and emotionally devastated, but often the stability of the marriage and family is also shaken. As the number of miscarriages increases, the condition becomes more severe, making the recurrence rate of miscarriage higher and higher. For example, the recurrence rate is 25% for those who have had one miscarriage, 30% for those who have had two miscarriages, 35% for those who have had three miscarriages, and more than 50% for those who have had more than four miscarriages. In view of the fact that there is no particular clinical manifestation to distinguish recurrent miscarriages of different causes, a comprehensive and systematic examination is often required for the diagnosis to clarify the causes and to provide targeted treatment. More than 60% of recurrent miscarriages are due to immune disorders. Before the establishment of reproductive immune testing methods, these women were almost “undetected” in the hospital, and thus did not receive appropriate and effective treatment. Recent developments in this field have revealed that immune miscarriages include both alloimmune disorders and autoimmune abnormalities, the former being due to high compatibility of the couple’s leukocyte antigens and the failure of the mother to produce protective “closed antibodies” to the embryo after conception, and the embryo is attacked by the mother’s immune cells and stops being born. For treatment, the husband’s lymphocytes can be used to actively immunize the wife to produce closed antibodies. The latter is due to the disruption of the patient’s own immune system, which produces a variety of antibodies against its own tissues and organs, which can also destroy the embryonic tissue and the placental cells that nourish the embryo, leading to its death. Treatment can be done with corticosteroids and immunoglobulins. The success rate of treatment for these patients has reached over 90%. We have successfully cured patients who had more than 10 consecutive miscarriages. Genetic factors cannot be treated Miscarriages caused by genetic factors include chromosomal abnormalities of the couple, chromosomal abnormalities of the fetus, and genetic abnormalities. Although chromosomal abnormalities in couples account for only about 5-8% of habitual miscarriages, there is no effective treatment at present, thus the recurrence rate is very high, and only about 20% of successful pregnancies, and half of these offspring have the abnormal chromosomes of their parents. Common chromosomal abnormalities include balanced translocations and inversions. Patients with balanced translocations have been known to have up to six consecutive miscarriages. However, it is worth noting that these patients may have a combination of immune disorders, which need to be checked at the same time to rule out, so that a normal fetus will not be preserved. (2) Fetal chromosomal abnormalities are caused by errors in the chromosomes of the fertilized egg during the division process after conception. It has been reported that the majority of embryos with episodic miscarriage (first miscarriage) have chromosomal abnormalities. (iii) The diagnosis of genetic abnormalities is currently difficult. Third, there are targeted treatments for endocrine disorders Endocrine abnormalities leading to miscarriage include gynecological endocrine and medical endocrine abnormalities: 1. Gynecological endocrine abnormalities: common ones include luteal insufficiency, hyperprolactinemia, polycystic ovary syndrome, etc. In women with luteal insufficiency, after pregnancy, the ovaries cannot produce enough progesterone to support the normal development of placental cells, and the embryo does not get enough nutrition and dies, which is manifested by slow rise in basal body temperature after ovulation, fluctuation, or insufficient height and short time limit, low progesterone level, treatment is relatively simple, and progesterone supplementation is the most effective method, which can be adjusted according to the level of progesterone in blood after conception and The dosage and treatment course can be adjusted according to the level of progesterone in blood after conception. Excessive prolactin mostly leads to non-ovulation and infertility, and even after conception, it is easy to miscarry, therefore, targeted treatment and fetal preservation must be given. Polycystic ovary syndrome is also often the cause of infertility and miscarriage, and aggressive fertility preservation therapy is very important in these women after conception. There have been cases where such patients conceived after arduous treatment, but miscarriage occurred due to neglecting the issue of fetal preservation, and later repeated treatments were unable to conceive again. 2. Endocrine abnormalities in internal medicine: mainly diabetic women and patients with abnormal thyroid function (including hyperthyroidism and hypothyroidism), if women with these diseases have been found, they should be treated until their condition is stable before considering pregnancy to avoid miscarriage. On the other hand, women with recurrent miscarriages should undergo relevant tests in this regard to avoid missing the diagnosis. Fourth, anatomical miscarriage occurs later Uterine anatomical abnormalities lead to recurrent miscarriage accounting for about 10%-15% of the miscarriages, which are characterized by mostly late miscarriages and embryos that are still alive at the time of miscarriage. The common causes are: cervical insufficiency, uterine developmental abnormalities (such as longitudinal uterus, unicornuate uterus, bicornuate uterus, saddle-shaped uterus, etc.), uterine fibroids or adenomyoma, and uterine adhesions. Diagnosis is based on ultrasound, hysterosalpingography, hysteroscopy and laparoscopy. Treatment is based on surgical correction, hysteroscopic surgery, or post-pregnancy cervical cerclage depending on the specific cause. V. Infections are common and indeterminate Patients with recurrent miscarriage have a high positive rate of about 50% for various infections of the reproductive tract, such as Mycoplasma solium, Chlamydia, bacterial vaginosis, Candida vaginitis, leukocytosis of vaginal discharge and poor cleanliness. However, these infections are not necessarily the cause of recurrent miscarriage, nevertheless, these women should be excluded and treated before conceiving again. Pre-thrombotic state should be taken seriously Some women have congenital or acquired disorders of blood clotting mechanism, which makes their blood clot too fast, called pre-thrombotic state. Although normally there is no clotting in the blood vessels to form a thrombus, after pregnancy, these women have thrombus formation in the placental vessels, blocking the blood circulation of the placenta and causing the embryo to die from ischemia. In the past, not enough attention was paid to recurrent miscarriage due to this condition, but recent studies have found that many of the recurrent miscarriages of unknown origin are due to a pre-thrombotic state, and anticoagulant therapy has had a good effect.