The role of CD4⁺CD25^bright regulatory T cells in the maintenance of pregnancy, premature rupture of membranes, and labor

Purpose: The aim of this study was to evaluale the changes of the regulatory T cell subset in peripheral blood caused by gestational age and premature rupture of membrains (PROM) with or without labor to verofy the role of regulatory T cells in-pregnancy. Patients and Methods: We investigated reglatory T cell digribution in the peripheral blood of pregnancies during the first trimester (group I, n = 2), the second trimester (group II, n = 12), and the third trimester without PROM and labor (group III, n = 15). In addition, we evaluated pregnancies in the third trimester complicated by PROM (group IV, n = 4) and labor with no complication by PROM (Group V, n = 5). Comparisons were made with non-pregnant controls (group VI, n = 4) using flow cytometry. Results: During uncomplicated pregnancy, the CD4⁺CD25^bright regulatory T cell population decreased with advancing gestational age (group I = 3.35 ± 0.47, group II = 2.91 ± 1.44, group III = 2.81 ± 1.36, group VI = 2.52 ± 0.71, p = NS). When we compared group IV with group III and V to evaluate the changes of the regulatory T cells with PROM, the CD4⁺CD25^bright regulatory T cell population was significantly decreased in group IV compared to group III (p = 0.001) and group V (p = 0.026). Conclusion: The present results revealed that the regulatory T cell population increased in early pregnancy but decreased in pregnancies complicated by PROM, indicating that regulatory T cells might be related to the maintenance of pregnancy.