The nk cells are the immune defense cells in the body and the normal level of natural killer cells is necessary to maintain a normal pregnancy. A high nk-cell level will affect conception and must be cured before pregnancy can occur without affecting the normal development of the fetus. nk-cells are the body’s first line of defense against tumors, but high nk-cells can cause infertility. Highly active natural killer cells are associated with autoimmune abnormalities, embryonic arrest and pregnancy complications. nk cells have no direct medical origin and are generally thought to be derived directly from the bone marrow and then mature depending on the microenvironment of the bone marrow. nk cells are overwhelmingly large granular lymphocytes and are particularly fast killing and lysing of many tumor cells. However, the cell value can only be a reference data, and there are chances of pregnancy.