Low levels of circulating T-regulatory lymphocytes and short cervical length are associated with preterm labor

Recent discoveries suggest that T-regulatory lymphocytes (Treg) might play an important role in the pathophysiology of preterm labor. The aim of this study was to assess the relationship among the levels of maternal circulating Treg cells, uterine cervical length, and the risk of preterm labor. Sixty women with regular contractions and/or cervical incompetence at 24-32 weeks' gestation were recruited into a prospective study. Each patient underwent transvaginal ultrasound examination of the cervical length, and regulatory T cells were quantified in peripheral blood samples by flow cytometry. Patients with cervical incompetence were prescribed vaginal progesterone until birth. Measurements of Treg levels and cervical length correlated with the timing of labor. The risk of preterm labor happening within 48 h of testing was demonstrated to be almost 35 times higher (OR = 35.21, CI 13.3; 214, p < 0.001) in the group with simultaneously low Treg values (<0.031 × 109/L) and a shortened uterine cervix (<17.5 mm), compared with the situation where both of these values were normal. Similar results were found in predicting preterm delivery before 34 weeks, or between 34 and 37 weeks. A statistically nonsignificant trend toward increased cervical length and increased Treg count was noted in the women on progesterone treatment. We show for the first time that the combined assessment of Treg cell count and cervical length is a much better predictor of preterm delivery than either parameter used on its own. This combined approach may offer clinical application in patients who present with risk factors for preterm labor.