Recurrent miscarriage (RM), defined as two or more consecutive losses of clinical pregnancy, affects about 1-2% of women. Etiologies can include uterine abnormalities, antiphospholipid antibody, chromosomal abnormalities, thrombophilic disorders, infections, autoimmune disease, and endocrine disorders. However, about 50% of RM have unknown etiology, and immunological abnormalities are presumed to play a large role. Although there is controversy over the role of natural killer cells (NK) in infertility and RM, a recent systematic review showed ...