Natural killer (NK) cells are immune cells found throughout the body. In fertility, two types are often discussed: peripheral blood NK (pbNK) cells and uterine NK (uNK) cells. uNK cells are abundant in the uterus and help support implantation and placental development. Although altered NK cell levels have been associated with infertility or recurrent pregnancy loss in some studies, it’s unclear whether they cause these problems, and NK cell testing remains controversial. Read more in my post NK cells in IVF.
