Reduced serum zinc concentration during pregnancy.

Serum zinc concentration and the partitioning of serum zinc between serum albumin and alpha 2-macroglobulin were measured in ten pregnant and five nonpregnant women fed controlled diets. The diet, prepared from blended foods, provided 16 mg/day of zinc. The pregnant women maintained total serum zinc concentrations which were approximately 19 to 27% lower than those of the nonpregnant controls. The decrease in serum zinc was associated with a decrease in serum albumin concentration. Although the pregnant women had lower concentrations of albumin-bound zinc and alpha 2-macroglobulin-bound zinc, the two groups maintained the same distribution of zinc in serum; approximately 75% was albumin-bound and 25% bound to alpha 2-macroglobulin. Given the expansion of maternal blood volume, a pregnant woman could have a larger circulating pool of zinc than a nonpregnant woman. The decline in serum zinc concentration with pregnancy appears to be a normal physiologic adjustment and is not necessarily indicative of inadequate zinc nutriture.