Tumor necrosis factor and pregnancy--a contribution to the immunology of reproduction.

Serum levels of the cytokine TNF (tumor necrosis factor) were determined in pregnant women during the first trimester and compared with levels in a control group of non-pregnant healthy women. A new immunoradiometric assay (IRMA) was used. In pregnant women we found a very low mean value of 2.5 pg/ml. The value was significantly higher 16.2 pg/ml in the non-pregnant group. This finding suggests suppression of macrophage activity which could favour the fetal allograft.