Changes in maternal plasma macrophage-colony stimulating factor levels during normal pregnancy.

An enzyme-like immunosorbent assay and a blood autoanalyser were used to determine macrophage-colony stimulating factor (M-CSF) levels and the absolute number and percentage of circulating monocytes in 80 normal women with singleton pregnancies at 12-40 weeks' gestation, and ten healthy non-pregnant volunteers. The mean values of M-CSF and absolute number and percentage of circulating monocytes of the control group were 367 U/ml (SD 43) and 389 x 10(6)/l (SD 180) and 5.3% (SD 1.7) respectively. In pregnancy, M-CSF was significantly higher than non-pregnant controls only after 28 weeks' gestation. The absolute number and the percentage of circulating monocytes increased significantly with gestation after 16 weeks. There was no significant association between the concentration of M-CSF and the number or percentage of circulating monocytes. These data suggest that during pregnancy there is an up-regulation of M-CSF and monocytes.