Purpose: Labor is thought to positively influence immune system development in the offspring, but studies investigating the impact of different modes of delivery on maternal immune system cells are scarce. Therefore, the aim of this study was to investigate the effect of labor on maternal peripheral blood T-cell subsets and on the recently described regulatory T and B cells. Methods: Cross-sectional study comparing the absolute counts and percentages of peripheral blood T-cell subsets (maturation and activation profiles) and regulatory T and B cells between healthy pregnant women who delivered their newborns via elective cesarean (no labor; n = 14) and those who had a spontaneous vaginal delivery (after labor; n = 18). The cells were characterized using flow cytometry. Results: We found that compared to the women who had elective cesareans, those who had spontaneous vaginal deliveries had significantly (P < .05) lower absolute counts of B cells (median [cells/L]: 146 [interquartile range, IQR = 49] vs 192 [IQR = 65]) and natural killer-like T (NKT-like) cells (median [cells/L]: 154 [IQR = 125] vs 224 [IQR = 117]) in the peripheral blood. No further significant differences, particularly in regulatory T and B cells, were identified between the study groups. Conclusion: Labor does not seem to have a major impact on maternal peripheral blood T-cell subsets or regulatory T and B cells.