Problem: Recurrent spontaneous abortion (RSA) is associated with immune imbalance at the maternal -fetal interface. Decidual immune cells and cytokines expressed at this interface regulate the response of the maternal immune system to the fetus. However, the populations and cytokine expression levels of these lymphocytes in miscarriage with normal and abnormal chromosome karyotypes remain unclear. Methods: We assessed the populations and cytokine expression levels of Natural Killer (NK), Natural Killer T (NKT), Helper T (Th) and Cytotoxic T (Tc) cells in the decidua of RSA by flow cytometry and simultaneously analyzed the fetal chromosome karyotypes of these miscarriages. Results: Flow cytometry showed no significant difference between RSA and normal pregnancy in the percentages of Th, Tc, NK, and NKT cells. Type-1 cells decreased significantly in the decidua of normal pregnancy, and NK2 and NKT2 cells increased significantly in the normal pregnancy group. We also found no difference in the lymphocyte composition and the proportion of types 1 and 2 subsets of the four lymphocytes in the decidua between RSA with abnormal chromosome karyotypes of villous trophoblasts (RSA-A) and RSA with normal chromosome karyotypes of villous trophoblasts (RSA-N), but the proportion of type-1 cells in both groups was significantly higher than that in normal pregnancy. Conclusion: No difference existed between the type-1 immune response of RSA in normal and abnormal chromosome karyotypes of villous trophoblasts. (C) 2018 Elsevier Inc. All rights reserved.