Research on membrane complement inhibitors (DAF, MCP, and CD59) has led to understanding of the regulation of complement system; however, their precise role and distribution remain speculative. In this study, we used an indirect fluorescent immunostaining to investigate the distribution of complements, MCP, DAF, and CD59, in the villi before the 10th week of pregnancy in 18 women. DAF and MCP were observed at the surface of syncytiotrophoblasts (ST) and extravillous trophoblast (EVT) in all subjects. They were observed in villous cytotrophoblast (VCT) in the subjects before the 8th week of pregnancy but were not observed in any subject after the 9th week. However, CD59 appeared in ST but never in VCT. MCP, DAF, and CD59 were observed in EVT. These findings indicated that these complement inhibitors played an important role in early pregnancy, and that CD59 continued to appear in early pregnancy, whereas the expression of MCP and DAF depended on the stage of pregnancy.