The incidence of habitual abortion in women of reproductive age is about 1%-5%, and the known causes include: 1) genetic factors: such as chromosomal abnormalities in the couple and chromosomal abnormalities in the embryo; 2) anatomical factors: such as uterine malformation, cervical insufficiency, uterine fibroids, uterine adhesions, etc.; 3) endocrine factors: such as luteal insufficiency, polycystic ovary syndrome, hyperprolactinemia, etc.; 4) infectious factors: such as rubella virus, cytomegalovirus, syphilis spirochete infection, etc.; 5) immune factors: such as closed antibody deficiency, etc., but the causes are still unknown in 30%-40% of patients. 5. Immune factors: such as closed antibody deficiency, etc., but there are still 30-40% of patients with unknown causes. Insulin resistance (IR) and/or hyperinsulinemia is an important pathogenesis of polycystic ovary syndrome (PCOS) with an incidence of 30%-75%, while several studies have shown a significantly higher rate of early spontaneous abortions in patients with PCOS. In the past, less attention was paid to the presence of insulin resistance in patients with habitual abortion, and only fasting glucose was routinely checked. Insulin resistance is a metabolic state in which the body’s physiological level of insulin promotes a decrease in the effectiveness of glucose absorption and utilization in organs, tissues and cells, that is, insulin levels are higher than normal or not lower than normal under normal or hyperglycemic conditions. The study showed that insulin resistance was significantly increased in the group of patients with habitual abortion compared to the control group, mainly in the form of increased glucose and insulin levels at 1h, 2h and 3h after OGTT, and increased area under the glucose curve and insulin curve, while there was no significant difference in fasting glucose and fasting insulin. This implies that checking fasting glucose and fasting insulin alone is not a good way to detect insulin resistance in some patients with habitual abortion. There is often a “separation” between the degree of insulin resistance in the liver and peripheral tissues (e.g., muscle, fat), with liver IR mainly showing elevated fasting glucose and peripheral tissue IR mainly showing elevated post-glucose load glucose. Patients with habitual abortion mostly show elevated glucose after glycemic load, indicating that their peripheral tissues are more insulin resistant than the liver, showing delayed peak glucose and insulin. In recent years, it has been shown that the application of insulin-sensitizing drugs such as metformin for PCOS patients before or during pregnancy can significantly reduce the rate of early spontaneous abortion, and studies have shown that the rate of early spontaneous abortion is significantly lower in PCOS patients who continue to apply metformin before and during pregnancy. A large body of domestic and international literature suggests that spontaneous abortion is associated with increased insulin resistance. Examination of fasting glucose and insulin in non-pregnancy revealed an increased incidence of insulin resistance in patients with a history of habitual miscarriage. A series of studies suggest that insulin resistance may be an independent risk factor for spontaneous abortion independent of PCOS and obesity. On the other hand, patients with PCOS have a higher incidence of insulin resistance, and it is possible that some patients do have PCOS but have not yet been diagnosed, so patients with a history of recurrent miscarriage should undergo further tests related to PCOS, such as androgen levels and vaginal ultrasound. The mechanism of insulin resistance causing early pregnancy miscarriage is not clear, but there may be the following reasons: hyperinsulinemia decreases the concentration of immunosuppressive glycodelin and insulin-like growth factor binding protein-1 (IGFBP-1) in early pregnancy, which increases the chance of early pregnancy miscarriage, and Glycodelin inhibits the immune response of the endometrium to the embryo and facilitates fertilization. Glycodelin inhibits the immune response of the endometrium to the embryo and facilitates implantation of the fertilized egg, IGFBP-1 facilitates adhesion of the embryo to the mother during the periimplantation period, and insulin negatively regulates its concentration, resulting in an increased risk of miscarriage. Hyperinsulinemia can also upregulate plasma fibrinogen activator inhibitor (PAI-1) levels, inducing chorionic villi thrombosis, affecting placental blood supply, causing trophoblastic dysplasia, and leading to miscarriage. For people with significant insulin resistance, reducing the level of insulin resistance through lifestyle improvement or medical interventions can have a positive impact on preventing recurrent miscarriages.