Spontaneous abortion is defined as a termination of pregnancy before 28 weeks and a fetus weighing less than 1000 grams. Any spontaneous miscarriage for 3 or more consecutive times can be called habitual miscarriage or recurrent miscarriage. Habitual miscarriage has a complex etiology and is prone to recurrence, and is actually a kind of infertility that is difficult to cure. The causes are as follows: a. Chromosomal abnormalities: 50-60% of spontaneous miscarriages are related to chromosomal abnormalities of the embryo. Chromosomal abnormalities include numerical abnormalities and structural abnormalities. Numerical abnormalities include chromosomal trisomies and monosomies. Structural abnormalities include: chromosomal translocations, chimerism, inversions, deletions and overlaps. Second, maternal systemic diseases 1, systemic infections during pregnancy, high fever (temperature greater than 38, 5 degrees) can cause uterine contractions leading to miscarriage. Bacteria and viruses (such as herpes simplex virus, cytomegalovirus, measles virus, etc.), toxoplasma and other infections can enter the fetal circulation through the placental barrier, causing fetal death and leading to miscarriage. 2.Severe anemia or heart failure can cause fetal hypoxia, resulting in miscarriage. 3, chronic nephritis or hypertension, placental infarction can lead to miscarriage. 4, endocrine abnormalities: abnormal thyroid function and failure to control diabetes can lead to miscarriage. 5, bad habits: excessive smoking, drinking, excessive coffee, drug use, etc. can lead to miscarriage. 6, trauma stimulation: severe shock, uterine trauma (surgery, direct impact, excessive sexual intercourse) can also lead to miscarriage. 7, mental factors: excessive tension, anxiety, fear, depression can also lead to miscarriage. Maternal reproductive system diseases 1, reproductive tract infection: bacteria, mycoplasma, chlamydia and rubella virus, cytomegalovirus, herpes simplex virus, human immunodeficiency virus, Toxoplasma gondii, etc. can lead to miscarriage. 2, maternal reproductive tract abnormalities and structural abnormalities: unicornuate uterus, bicornuate uterus, double uterus, uterine longitudinal septum, can affect the uterine blood supply and the intrauterine environment, resulting in miscarriage. ashemem syndrome, due to deep scraping of the uterine cavity caused by trauma, infection and other causes of uterine adhesions and fibrosis, can affect the embryo implantation, resulting in habitual miscarriage. Another uterine cavity insufficiency, severe cervical laceration, short cervical canal, or relaxed inner cervical opening are the main causes of late stage habitual abortion. In addition, uterine fibroids can also affect the intrauterine environment, leading to habitual miscarriage. 3. Luteal insufficiency: low progesterone can cause poor metaphase response to pregnancy, which can affect the implantation and development of pregnant eggs and lead to miscarriage. 4, Polycystic ovary syndrome: PCOS for short, high concentration of LH may lead to premature completion of the second meiosis of the oocyte, premature maturation of the oocyte and ovulation of “old eggs”, thus affecting the fertilization and implantation process. 5, hyperprolactinemia: PRL can directly inhibit the proliferation and function of luteal granulosa cells, the main clinical manifestation of HPRL is amenorrhea and overflow of milk. 6, abnormal immune function: autoimmune type of habitual abortion, mainly related to the anti-phospholipid antibody syndrome and the phase difference of antiphospholipid antibodies (anti-cardiolipin antibody). Anti-phospholipid antibody syndrome leads to thrombosis and embolism mainly through various pathways such as activation of vascular endothelium and platelets, and can also lead to miscarriage by directly damaging trophoblast cells to damage the embryo. Additional related factors are: histocompatibility antigens, blood group antigens (ABO and RH), anti-sperm antibodies, anti-endometrial antibodies, etc. Unknown causes (alloimmune factors): miscarriages that exclude the above etiologies are associated with alloimmunity. For miscarriage with alloimmunity modern reproductive immunology considers that pregnancy is a successful semi-allogeneic transfer process in which the pregnant woman shows immune tolerance to intrauterine embryo grafts without rejection due to a series of adaptive changes in her own immune system, allowing the pregnancy to continue. In the maternal serum, there is one or several confinement factors, also called confinement antibodies, that inhibit immune recognition and immune response. If there is an imbalance in the immune tolerance status, the embryo can suffer an immune strike from the mother and be rejected, leading to miscarriage. At present, the more commonly used method of detecting closed antibodies is the micro anti-husband lymphocytotoxic test, negative results indicate the lack of closed antibodies in the woman’s serum, prone to habitual abortion. Fourth, environmental factors arsenic, lead, formaldehyde, benzene, chlorobutadiene, ethylene oxide and other excessive exposure can cause miscarriage. Radiation fluoroscopy, radiography and other examinations, and many drugs can lead to fetal malformation and miscarriage. In addition, whether prolonged exposure to radiation from computers, cell phones, microwave ovens, car exhaust, sauna heat, airplane noise, perm and hair dye can cause miscarriage is to be further confirmed. What tests are required for miscarriage? Three or more consecutive spontaneous miscarriages are called habitual miscarriages. If the medical history is accurate, the following tests should be done for habitual miscarriage: gynecological examination to understand whether there is tearing of the cervix and the size and shape of the uterus; basal metabolism measurement, serum T3 and T4 to understand thyroid function; basal body temperature measurement, premenstrual endometrial tissue examination to understand the secretion function of the ovarian corpus luteum; karyotype analysis; ultrasound examination to clarify whether there is cervical atresia; hysterosalpingogram to diagnose Uterine developmental abnormalities, especially uterine malformations and uterine adhesions; semen examination. If one of the couple has chromosomal abnormalities, it is better to avoid pregnancy. Once the pregnancy, prenatal diagnosis should be made in a timely manner, and termination of pregnancy should be carried out immediately if abnormalities are found. 2. If the luteal function is insufficient, progesterone can be given as supplement. If there is a possibility of conception, progesterone should be given 10-20mg/d from the 3rd to 4th day of elevated basal body temperature, and continue the treatment until the 9th to 10th week of pregnancy after the pregnancy is confirmed. 3. For subclinical hypothyroidism, appropriate amount of thyroxine treatment should be given. 4. If the vaginal or cervical discharge of the female partner and the semen of the male partner are positive for bacterial culture, treat them accordingly according to the drug sensitivity test until they are cured. Use penis condom for contraception during treatment. 5.Uterine longitudinal septum and uterine fibroids should be surgically corrected before pregnancy. 6.Incomplete cervical atresia, cervical suture should be performed after pregnancy. Generally, it is recommended to perform the procedure under general anesthesia after excluding fetal abnormalities or stillbirths at about 16 weeks of mid-pregnancy. Regular postoperative follow-up is recommended. If there are signs of miscarriage or preterm labor, the stitches should be removed promptly to avoid serious damage to the cervix. If fetal preservation is successful, admission to the hospital for delivery is required 2 to 3 weeks before the expected date of delivery. Immediately after labor, the sutures are removed to await delivery.