Spontaneous miscarriage is a heartbreaking topic, and the most common question couples ask during their visits is, “What caused my miscarriage?” “Is the miscarriage due to the sperm or the egg?” “Our test results were normal, what’s the next step?” In the face of these unanswered questions, let me try to talk to you about miscarriage. The etiology of miscarriage is complex and uncertain. In domestic and international guidelines and consensus, the etiology of miscarriage is mostly summarized as: 1) genetic factors; 2) uterine structural factors; 3) endocrine factors; 4) immune factors; 5) thrombotic tendency; 6) infectious factors, etc. However, in fact, except for chromosomal abnormalities in couples or fetuses, other etiologies are often difficult to identify and the evidence of clinical testing is not very sufficient, so our ability to determine the etiology is limited. Therefore, based on the available literature, and our knowledge of spontaneous abortion, and our experience in managing it, we provide the following consultation views. 1. Chromosomal examination of both couples is the first step If the chromosomes of one of the couples are balanced translocations (including Roche translocation), the probability of signal balance of fetal chromosomes is only 1/9, which means nearly 90% possibility of spontaneous abortion, and some couples can encounter an occasional live birth. In some couples, the chromosomal abnormalities are polymorphic karyotypes. The most common ones are inter-arm inversions, large Y chromosomes, and chromosome followers, which have a high incidence in the population, for example, the incidence of inter-arm inversions of chromosome 9 is 1%, which is not necessarily related to miscarriage. Some doctors may think that the occurrence of aneuploidy in miscarriage is a probable event, and since miscarriage has already occurred, the examination of villi chromosomes cannot change the outcome of miscarriage, so there is no need to do it. The incidence of chorionic villi aneuploidy in miscarriage is about 50%, and with the results of this test, at least half of the causes of this miscarriage can be answered. Without evidence of a chorionic chromosome test, doctors are often unable to answer questions about the cause of this miscarriage. If the chorionic chromosome is aneuploid and occurs consecutively, it indicates an increased risk of miscarriage due to chromosomal abnormalities in the fetus of the next pregnancy, without much examination of other causes, and if necessary, third generation IVF PGS can be recommended; if the chorionic chromosome test is an integer karyotype, it means that the cause of this miscarriage is not chromosomally related, and it is necessary to continue the examination of other etiologies. 3. Endocrine causes are also important Endocrine causes related to miscarriage include: hypothyroidism, insulin resistance, obesity, hyperprolactinemia, follicular dysplasia and luteal insufficiency. Therefore, screening for the etiology of recurrent miscarriage includes these indicators. The doctor will advise the patient to reduce weight, establish a good lifestyle, correct thyroid function and prolactin levels, and promote ovulation and luteal support if necessary. 4. Examination of the uterine cavity and endometrial morphology is relatively easy Ultrasound examination of the uterine cavity and endometrial morphology can be performed at the same time as the ovulation monitoring cycle. It is relatively easy to see uterine malformations, endometrial adhesions, intrauterine polyps, fibroids, and other problems. 5. Autoimmune and thrombotic tendencies are further tests If none of the above causes are found to be abnormal, only then are autoimmune and thrombotic indicators further examined, including a range of autoimmune antibodies, coagulation function, and other items of thrombophilia. Other than confirming a diagnosis of antiphospholipid syndrome, these types of tests are not necessarily conclusive diagnostic evidence and can be referred to. The screening for blocking antibodies is highly controversial and the test is imprecise and can only be used as a reference for reference. The history of spontaneous abortion is a complex issue, and many presumed etiologies do not necessarily have diagnostic evidence. In the absence of conclusive evidence, the etiology can only be broadly presumed, examined and managed. Some patients can only try to conceive while waiting for a good time to conceive, or while waiting for evidence of etiological diagnosis to appear.