Maternal-fetal immunity and recurrent spontaneous abortion

Recurrent Spontaneous Abortion (RSA) is a common pregnancy complication, that has multifactorial causes, and currently, 40%-50% of cases remain unexplained, referred to as Unexplained RSA (URSA). Due to the elusive etiology and mechanisms, clinical management is exceedingly challenging. In recent years, with the progress in reproductive immunology, a growing body of evidence suggests a relationship between URSA and maternal-fetal immunology, offering hope for the development of tailored treatment strategies. This article provides an immunological perspective on the pathogenesis, diagnosis, and treatment of RSA. On one hand, it comprehensively reviews the immunological mechanisms underlying RSA, including abnormalities in maternal-fetal interface immune tolerance, maternal-fetal interface immune cell function, gut microbiota-mediated immune dysregulation, and vaginal microbiota-mediated immune anomalies. On the other hand, it presents the diagnosis and existing treatment modalities for RSA. This article offers a clear knowledge framework for understanding RSA from an immunological standpoint. In conclusion, while the "layers of the veil" regarding immunological factors in RSA are gradually being unveiled, our current research may only scratch the surface. In terms of immunological etiology, effective diagnostic tools for RSA are currently lacking, and the efficacy and safety of immunotherapies, primarily based on lymphocyte immunotherapy and intravenous immunoglobulin, remain contentious.