Uterine natural killer cells exert their function by production of high levels of cytokines such as granulocyte-macrophage colony stimulating factor (GM-CSF), colony stimulating factor-1 (CSF-1) and interleukin-2 (IL-2). Recurrent miscarriage (RM) is a stressful condition for both patients and clinicians. As uterine natural killer (uNK) cells share many similar properties with peripheral blood NK cells, their population in the blood has been reported to be associated with RM. Steroids are used as anti-inflammatory agents to try to improve success of implantation, as aside from the immunology of pregnancy, there could be other inflammatory processes in the practice of in-vitro fertilization (IVF) such as stimulation from the intrauterine catheter during embryo transfer. As with RM, immunomodulation therapies have been tried to suppress NK cell activity. A recent meta-analysis of three trials shows that IvIg treatment significantly increases the live-birth rate in patients who fail IVF.