Early predictive value of maternal peripheral blood circulating immune cell counts for spontaneous preterm birth

To investigate the profiles of circulating immune cells in maternal peripheral blood in spontaneous preterm birth (SPB) and evaluate their potential for the early prediction of SPB, thereby providing a basis for clinical screening of preterm birth risk.

This study included 43 women with SPB (SPB group) and 129 women who delivered at term (term delivery group). Baseline characteristics (e.g. age, pre-pregnancy body mass index, obstetric history) were compared between the two groups. Peripheral blood samples were collected at 26 ± 1 weeks of gestation during routine antenatal examination. The proportions of T cells, B cells, natural killer (NK) cells, CD4⁺ T cells, and CD8⁺ T cells in peripheral blood were measured by flow cytometry, and the CD4⁺/CD8⁺ ratio was calculated. Variables with significant intergroup differences in baseline data were entered into multivariate regression analysis to identify independent associations between immune cell parameters and SPB. Three predictive models were constructed using backward stepwise logistic regression: an immune cell model, a clinical characteristics model, and a combined model (clinical characteristics + immune cells). The predictive performance of each model was evaluated using the area under the receiver operating characteristic curve (AUC), sensitivity, and specificity.

Significant between‑group differences were observed in the proportion of multiparous women and history of preterm birth, with a trend toward significance for history of abortion. Cervical length was significantly shorter in the SPB group. Compared with the term delivery group, the SPB group exhibited significantly higher percentages of NK cells and CD8⁺ T cells, and a significantly lower CD4⁺/CD8⁺ ratio. Multivariate regression analysis indicated that a lower CD4⁺/CD8⁺ ratio and a higher NK cell percentage were independently associated with SPB. Among the three predictive models, Model 1 (immune cells) and Model 2 (clinical characteristics) showed comparable AUC values of 0.777 and 0.775, respectively. Model 3 (combined) demonstrated significantly superior predictive performance, with an AUC of 0.857, a sensitivity of 74.42%, and a markedly improved specificity of 82.95%.

Women with SPB exhibit features of immune imbalance characterized by elevated NK cells, elevated CD8⁺ T cells, and a decreased CD4⁺/CD8⁺ ratio. The CD4⁺/CD8⁺ ratio and NK cell percentage were independently associated with SPB.