Preconceptional natural-killer-cell activity as a predictor of miscarriage.

There is no immunological test for the prospective identification of alloimmune causes of miscarriage. We investigated whether activity of natural killer cells was predictive of subsequent abortion in women who had had unexplained recurrent abortions and had received no treatment. 24 women with high preconceptional NK activity, defined as mean plus 1 SD of NK activity of 47 controls, had a significantly higher abortion rate in the next pregnancy than 44 women with normal levels of NK activity (71 vs 20%; relative risk 3.5; 95% CI 1.8-6.5). The preconceptional evaluation of NK activity in women with recurrent miscarriages may thus be predictive of the risk of pregnancy loss at the next conception.