Objective: Thrombin is released from decidual hemorrhage which occurs frequently in early miscarriage. GnRH and GnRHR are found in placental tissue during human pregnancy. GnRH/GnRHR signaling at the maternal-fetal interface increased hCG production. Progesterone plays an important role in the maintenance of pregnancy. Progesterone receptor is expressed regardless of GnRH/GnRHR signaling in human trophoblasts. This aimed to evaluate the roles of thrombin on hormonal factors found at the maternal-fetal interface in early pregnancy. Methods: Decidual stromal cells (DSCs) in early pregnancy and HTR-8/SV neo cells were incubated for 48 hours with thrombin (1 U/mL, 2.5 U/mL, 5 U/mL). The expressions of GnRH-I, GnRH-II, hCG, and PR-AB and PR-B were measured by quantitative real-time reverse transcriptase-polymerase chain reaction. Each experiment was conducted in triplicate and repeated a minimum of 3 times. Statistical analyses were performed using SigmaStat 3.5. Significant differences in the expression of genes between each group and the control (fold value, mean ± SE) were calculated using t test and Mann-Whitney Rank Sum Test. P<0.05 was considered statistically significant. Results: In DSCs and HTR-8/SV neo cells, expression of GnRH-I mRNA increased significantly in each group compared with control, whereas expressions of GnRH-II and hCG mRNA were not different. In HTR-8/SV neo cells, expressions of PR-AB and PR-B mRNA and the ratio of PR-B to PR-AB mRNA level did not differ in any of the groups as compared to the control. Conclusion: This study demonstrate that in early pregnancy, thrombin has different effects on hormonal factors related to pregnancy maintenance.