As an autoimmune disease, the etiology of rheumatoid arthritis in pregnancy is still unknown and may be related to genetic and infectious factors. The disease is non-infectious and has no means of transmission. It occurs in women with a family history of rheumatoid arthritis, women with viral infections, and women who smoke on a daily basis, and can be triggered by factors such as cold, dampness, excessive fatigue, mental stimulation, and smoking. Main causes 1, genetic factors: the common prevalence of homozygous twins is 15% ~ 30%, heterozygous twins is only about 5%. The prevalence rate of first-degree relatives of patients is 16 times higher than that of the normal population, and rheumatoid arthritis is closely related to the HLA-DR4 phenotype.2. Infectious factors: microbial infections may be the factors causing the onset of disease or triggering the immune response, and Lyme disease spirochete can cause rheumatoid arthritis-like manifestations.EBV can stimulate B lymphocytes to produce immunoglobulins including rheumatoid factor, and high titers can be detected in the serum of 80% of the patients with rheumatoid arthritis. High titers of anti-EBV antibodies are detected in the serum of 80% of patients with rheumatoid arthritis. T-lymphocytes in the synovium of patients with rheumatoid arthritis produce an immune response against 65 heat shock protein. This protein belongs to a family of stress proteins that can be expressed by a variety of bacteria and can be found in the synovium, vascular opacities, or cartilage binding sites. Second, triggering factors such as smoking, cold, humidity, excessive fatigue, mental stimulation and other factors can induce the disease.