Natural killer cell activity in women with recurrent miscarriage: Etiology and pregnancy outcome

This study aimed to evaluate whether natural killer (NK) cell activity was associated with the etiology of recurrent miscarriage (RM), and to evaluate the predictive value of NK cell activity for outcomes of following pregnancies in women with RM. Peripheral NK cell activity was measured in 160 non-pregnant women with a history of two or more miscarriages. This activity was compared according to the etiology of RM and to pregnancy outcomes in women who became pregnant. NK cell activity in women with unexplained RM was significantly higher than that in those with known etiologies of RM. NK cell activity in women whose next pregnancies ended in miscarriage of fetuses with a normal chromosome karyotype (MN) was higher than that in those with live births (p < 0.05). Women with NK cell activity ≥33% had a higher risk for MN (relative risk 3.4, 95% confidence interval 1.3-8.7). An increase in peripheral NK cell activity was associated with MN. This increase might be involved in the pathophysiology underlying RM.