The peripheral blood natural killer (pNK) cell CD69+ activation was markedly reduced in the miscarriage cohort, in both percentage expressions (1.6 vs 5.4%, P = 0.024) and concentrations (5.7 vs 15.7 cells/μL, Table 3) and an increase in CD57+ NK cells (comprising both CD16+CD56dim pNK and CD3+CD56dim NKT) (45.4 vs 38.9%, P = 0.025) (Fig. 2). This evidence concerns the gene CD69 and spontaneous abortion.