Research progress of immune balance and genetic polymorphism in unexplained recurrent abortion

The etiology of recurrent spontaneous abortion (RSA) is extremely complex, as there are 40–50% of patients with unexplained miscarriages, known as unexplained RSA (URSA). URSA affects approximately 1–2% of females of childbearing age and has a massive impact on the physical and mental conditions of both patients and their families. The pathogenesis of the disease remains unclear, making its treatment complicated. In recent years, considerable progress has been made in the exploration of the URSA immune balance mechanism and it has been universally acknowledged that a balanced immune response (as abnormal immunity) may be the root cause of poor pregnancy outcomes. This review discussed and summarized the effects of immune cells and blocking antibodies (BAs) on URSA based on the current state of knowledge in this area. Additionally, molecular genetics also plays an essential role in the incidence rate of URSA since the role of genetic polymorphism in the pathogenesis of URSA has been thoroughly studied. Nonetheless, the outcomes of these studies are inconsistent, particularly across populations. This paper reviewed previous studies on URSA and maternal genetic polymorphism, focusing on and synthesizing the most important findings to date, and providing diagnostic recommendation for URSA patients with clinical symptoms.