High NK Cell Activity in Early Pregnancy Correlates with Subsequent Abortion with Normal Chromosomes in Women with Recurrent Abortion

PROBLEM: The aim of this study was to assess the role of natural killer (NK) cells in pregnant women with a history of recurrent spontaneous abortion (RSA). METHOD OF STUDY: Consecutive 66 pregnant women with a history of RSA were prospectively assessed for peripheral NK cell activity, percentage of the NK cell subsets, and subsequent pregnancy outcome. RESULTS: NK cell activity in women with subsequent live birth (group I) at 4–5 gestational weeks (GW) (mean±SD, 32.5±12.3%) significantly decreased at 6–7 GW (28.1±12.1%) and at 8–9 GW (28.0±11.8%). NK cell activity in women with subsequent abortion with normal chromosomes (group II) at 6–7 GW (41.2±19.0%) was significantly higher than that in group I women, while NK cell activity at 6–7 GW in women with subsequent abortion with abnormal chromosomes (group III) was the same as the level in group I women. CONCLUSIONS: High NK cell activity at 6–7 GW correlates with subsequent abortion with normal chromosomes.