Redistribution of plasma zinc between albumin and alpha 2-macroglobulin in pregnancy.

A cross sectional study involving 12 non-pregnant and 71 pregnant women was undertaken to determine the effect of pregnancy on the concentration in the plasma of zinc and copper and the binding of zinc to plasma proteins. The results confirmed the relationship observed by others between reduced zinc and increased copper concentrations in the plasma of pregnant women. These changes occurred during the first and second trimesters of pregnancy. The concentrations of plasma albumin-bound zinc and alpha 2-macroglobulin-bound zinc were observed to decrease 27.5% and 52.1%, respectively, during the second and third trimesters of pregnancy. During the second and third trimesters of pregnancy a redistribution of zinc occurred within the total plasma zinc pool between albumin and alpha 2-macroglobulin. In the process, the contribution of albumin-bound plasma zinc pool was increased 16.2%, whereas the contribution of alpha 2-macroglobulin-bound plasma zinc was decreased 31.6%. The former is considered more "dynamic" than the latter and the observed shift of zinc within the plasma pool to the albumin-bound state, during pregnancy, may represent an adaptive response designed to offset any adverse effects of reduced maternal plasma zinc concentrations on the developing fetus.