Maternal T cells and human pregnancy outcome.

Mothers who had just delivered babies of normal birthweight showed significant reductions in the numbers of circulating T and B lymphocytes and of the CD4 T lymphocyte subset. This is consistent with the immunosuppression that occurs in a normal pregnancy. In contrast, the mothers of low birthweight infants did not show these reductions and had circulating lymphocyte numbers not significantly different from normal controls. This suggests that a component of intra-uterine growth retardation may be immunopathological, owing to a failure of the immunosuppressive mechanisms of pregnancy that might normally prevent the fetus from immunological attack.