Recent study has suggested that innate immune system might play an important role in pregnancy progression. In this study, to investigate whether NK cells and NKT cells, instead of T cells, are the dominant populations of peripheral blood in early pregnancy, flow cytometry was used to detect the percentage and intracellular cytokine expressions of T cells, NK cells, NKT cells in peripheral blood of non-pregnant women and early pregnant women.In our result, the percentages of NK cells and NKT cells were significantly increased in pregnancy compared to non-pregnancy. However, the percentage of T cells was not changed. We did not detect the Th2-dominance of total lymphocytes or T cells in peripheral blood of early pregnant women and there were also no significant changes of type 1 and type 2 cytokines in T cells, but IFN-γ production in both NK and NKT cells was decreased in early pregnancy. These results suggest that the innate immune system including NK cells and NKT cells should play a pivotal role in pregnancy progression. Type 1/type 2 shift mechanisms in innate immune system during the human early pregnancy should be paid more attention.