Abstract: Decidual natural killer (dNK) cells accumulate in the maternal decidua during pregnancy and are found in direct contact with fetal trophoblasts. However, the mechanisms of dNK cells during pregnancy are mostly unknown. By secreting cytokines/chemokines and angiogenic factors, dNK cells participate in normal placentation including feto-maternal tolerance, spiral artery remodeling and neovascularization during decidualization in a successful pregnancy. In recent years, dNK cells have been found to be closely related to the occurrence and maintenance of normal pregnancy. It has also been found that abnormal changes of DNK cell cytology and immunology and other aspects are common in complications of pregnancy such as recurrent spontaneous abortion, pre-eclampsia, etc. This review intended to summarize and discuss recent data that may challenge the conventional view of dNK cells, including quantitative, phenotypic, secretory cytokines and angiogenic factors, and possible mechanisms of dNK cells in the pathogenesis of pregnancy complications. To elucidate latest knowledge on dNK cells, may guide the prevention and treatment of complicated pregnancies.

Key words: Killer cells, natural, Decidua, Abortion, habitual, Pre-eclampsia