A longitudinal study of leucocyte numbers and mitogenesis during the last ten weeks of human pregnancy.

Leucocyte numbers rose consistently in normal primigravid women sampled repeatedly during the last ten weeks of pregnancy. The increase in total leucocyte count was significant from 35 weeks gestation to delivery and was directly related to an increase in neutrophils, while mononuclear cell numbers remained unaltered. In addition to the pregnancy associated neutrophilia there was a further increase in neutrophil counts at delivery. Using whole blood and purified leucocytes in culture, it was confirmed that pregnancy plasma contains suppressor factors which inhibit mitogenesis with PHA or Con A. There was no significant change in individual women's whole blood mitogenic response at any time during the sampling period except at delivery when there was a significant decrease. Culture of washed cells from pregnant women in non-pregnancy plasma restored their mitogenic response to levels found in non-pregnant control women, except at delivery when there was evidence of a cell-associated impairment of function. Purified leucocyte cultures from individual women sampled repeatedly from 30 weeks gestation to delivery gave variable responses although it was still possible to identify pregnancy-related plasma suppressor factors and delivery-associated impairment of leucocyte function in vitro.