Does progesterone administration in preterm labor influence Treg cells?

Objectives: The aim of this study was to determine if the actions of progesterone on preterm labor are accomplished through modulation of the percentage of regulatory T-cells (Treg). Methods: The study was a cohort pilot study made in a single center tertiary obstetrical unit with women in preterm labor arrested with tocolytic treatment. Variation of the number and percentage of Treg cells obtained from peripheral blood samples of women with preterm labor were calculated by flow cytometry, before and after progesterone administration. Results: In the paired samples for each patient, there was a significant difference in the Treg cell pool after progesterone treatment, with an increase in both their percentage (48.9 vs. 53; P = 0.07) and absolute number (14.8 vs. 56.5 cells/μL; P = 0.046). Conclusions: This research demonstrated a considerable increase in the Treg cell pool after progesterone treatment. This indicates a possible mechanism for progesterone treatment benefits in preterm labor, potentially increasing its more rational use.