Tarek S Beytamouni and Esther Ghanem
Suppression of the maternal immune system to tolerate the fetal alloantigens during implantation results in an immunological paradox. The initial implantation process is characterized by the migration of interstitial extravillous trophoblasts (EVT) into the endometrial wall and is supported by maternal uterine natural killer (uNK) cells. Any impairment of uNK support can ultimately lead to pregnancy loss. In this review, we discuss current information on the role of uNK cells in healthy human pregnancy and their importance in maintaining controlled endometrial invasion by EVT.