Within-woman change in regulatory T cells from pregnancy to the postpartum period.

Regulatory T cells (Treg cells) are an important area of investigation in human health and disease. In this study, the trajectory of percentage of Treg cells (defined as CD4+CD25+Foxp3+CD127--lymphocytes) was measured in the blood of 208 women during pregnancy and up to three additional times in the postpartum period (1, 6 and 12 months postpartum). Whether the trajectory was affected by gravidity, parity, neonatal sex, pet exposure, maternal atopic and asthma status, smoking, maternal race or other pregnancy factors was examined. Multilevel models were fit using full maximum likelihood methods and included both random and fixed effects. Overall, percentages of Treg cells increased from the prenatal to the postpartum period. Among women who were not atopic, nulliparous women had lower percentages of Treg cells over time compared with parous women. Atopic women with pets in the home during pregnancy had lower percentages of Treg cells than atopic women who did not have pets. The trajectory was not affected by the other factors investigated. We conclude that within-woman change in percentages of Treg cells may vary by time in relation to delivery, as well as by maternal atopic status and exposure to pets and number of prior births. The data did not indicate an overall decline in Treg cells in the postpartum period. Future work to better identify the role of Treg cells in successful pregnancy would ideally include a set of well characterized women sampled serially starting prior to pregnancy and throughout the postpartum period.