Changes in lymphocyte subsets during normal pregnancy.

Peripheral blood lymphocytes from healthy women were studied during pregnancy and postnatally, and were compared with lymphocytes from an age-matched non-pregnant control group. Compared with non-pregnant women, the total white cell count was significantly increased at all pregnancies and also post-partum. In pregnancy the absolute number and percentage of T lymphocytes was slightly elevated while almost no changes in B cells were found. No significant changes were found in the percentage of suppressor/cytotoxic (CD8+), of helper/inducer (CD4+) T lymphocytes, nor of CD4+/CD8+ ratio at any stage of pregnancy and puerperium. The most remarkable changes of the immune system occurred in the group of HLA-DR+ and CD56+ activated T cells. The cell numbers showed a significant increase in the first trimester (< 14 weeks) and decreased slightly from stage to stage. Lower values in NK (natural killer) cells and higher levels of IL-2 receptor positive T lymphocytes did not reach significant levels of change.