Background: The first trimester of pregnancy remains an unknown immunological adaptation. Cytokines and syncytiotrophoblast microvesicles (STBM) have been identified as key factors involved in the maternal immune adaptation. This study therefore aims to determine the levels of T helper cell 1 (Th1) and 2 (Th2) associated cytokines TNF-α and IL-6 in relation to the relative concentration of STBM's in maternal circulation. Materials and Methods: Plasma samples from normotensive pregnant women in the first trimester of pregnancy were obtained. The concentrations of TNF-α and IL-6 were determined using ELISA. STBMs were determined by isolating microvesicles in maternal circulation and quantifying the concentration of PLAP using ELISA. Results: TNF-α, IL-6 and STBMs remained at constant levels in weeks 5-10 of gestation. In weeks 11-12 of gestation, TNF-α increased with a decrease in IL-6 and STBMs. Ratio of TNF-α/IL-6 remained constant in weeks 5-6 and significantly increased in weeks 11-12 of gestation. A positive correlation between TNF-α and IL-6 was obtained in weeks 6-10 and a negative correlation in weeks 11-12 of gestation. In addition, a positive correlation between STBMs & TNF-α was obtained and negative correlation between STBMs and IL-6. was observed Conclusion: The relationship between TNF-α/IL-6 and STBMs suggests that syncytiotrophoblast microvesicles may have a role in cytokine production and in the maintenance of the Th1/Th2 immune adaptation in normal pregnancy.