The function, peripheral blood expression, and physiologic importance of IL-17 is not well established. Detection of IL-17 in sera and plasma samples from patients with pre-eclampsia has been reported with inconsistent results. To establish the l levels of the IL-17 at peripheral level, we studied prospectively a cohort of 13 healthy pregnant women. To evaluate the changes in serum levels of IL-17 in healthy pregnant women in a prospective cohort. Thirteen healthy pregnant women were prospectively followed to evaluate serum levels of IL-17. Each patient was evaluated at each trimester. IL-17 levels were measured by ELISA. The statistical analysis was done using repeated measures anova and Bonferroni's multiple comparison test. IL-17 levels were significantly increased from first trimester with a mean of 14.61 up to 31.78 pg/mL at third trimester (P < 0.05), but when detectable, they were almost identical range in all trimesters. We propose that IL-17 levels in healthy women are present with very similar range levels during the whole pregnancy but the average is increased during the third trimester maybe as a part of the complex network of cytokines as a result of implantation, fetal development, and labor process itself. © 2010 John Wiley & Sons A/S.