Spontaneous abortion: It is a termination of pregnancy that occurs before 20 weeks of gestation. Recurrent miscarriage: 3 or more consecutive spontaneous abortions. Current studies have found that the incidence of etiology in patients with more than 2 spontaneous abortions and 3 spontaneous abortions is essentially the same. Therefore, etiological examination should be performed after 2 consecutive spontaneous abortions, especially in women of advanced age, so that the cause can be found and the patient can be treated to avoid the physical and psychological trauma caused by multiple abortions. The probability of 3 or more spontaneous abortions in the normal population is 1 to 2 %. The probability of having 2 consecutive miscarriages is 5%. In fact, the probability of spontaneous abortion in women of childbearing age is 50%-60%, mostly manifested as slightly delayed menstruation, increased menstruation or normal menstruation, because the fertilized egg stops developing very soon after it is laid in the endometrium. In the case of spontaneous abortion, the incidence of clinical symptoms such as a clear history of menopause, abdominal pain, vaginal bleeding, etc., is 10%-15%. In addition to the clear causes, modern lifestyle changes, delayed childbearing age, environmental pollution, food safety and other issues may be the causes of normal pregnancy, so we should pay enough attention to them. The probability of spontaneous abortion is directly related to the age of both sexes. For women, the spontaneous abortion rate is 8.9% between the ages of 20 and 24, and increases after the age of 30, rising to 74.7% after the age of 45. This is because as we age, ovarian function declines, egg quality decreases, the incidence of chromosomal abnormalities in the embryo increases, and hormone levels and endometrial conditions become unfavorable for the continued growth and development of the embryo. Male partner: After age > 40, the risk of miscarriage for the loved one also increases, which may be related to a decline in sperm quality, including mutations in the sperm’s own genes and aneuploidy. There are several major categories of etiology: chromosomal factors Uterine anatomical abnormalities: longitudinal uterus, bicornuate uterus, unicornuate uterus, uterine dysplasia, uterine adhesions, cervical insufficiency, uterine fibroids. Reproductive tract infection factors Endocrine abnormalities: luteal insufficiency, polycystic ovary syndrome, hyperprolactinemia, thyroid dysfunction, diabetes mellitus. Pre-thrombotic state Immune disorders Tests required for both sexes at the hospital: Male partner: semen analysis + karyotype analysis Female partner: karyotype analysis, gynecological ultrasound, TORCH (toxoplasma, rubella virus, cytomegalovirus, herpes simplex virus), mycoplasma, sex hormones, A function, blood glucose, coagulation series, reproductive immune antibodies, closed antibodies.