Programmed cell death protein 1 (PD-1) is an important immune checkpoint molecule that regulates the immune system and promotes autoimmune tolerance by regulating the immune response to human cells and inhibiting the inflammatory activity of T cells. Recent studies have found that PD-1 plays an important role in regulating maternal and fetal immune tolerance and maintaining pregnancy. This article reviews the source, distribution, and biological characteristics of PD-1 and its role in normal pregnancy as well as the research progress of abnormal PD-1 expression in the pathogenesis of pregnancy-related diseases such as pre-eclampsia and recurrent abortion to provide a theoretical basis for early prevention, early diagnosis, and timely treatment.