1. To investigate the possible effect of iron ingestion on maternal zinc status, one group of women was given 94 mg of iron per day as ferrous sulphate with multivitamins during the second and third trimesters of their pregnancies and another, control, group was given a placebo of multivitamins without iron.
2. The subjects given iron developed significantly lower plasma zinc concentrations than those in the control group. This effect on zinc was maximal by 6 weeks, whilst that on maternal iron status was slower.
3. There was no parallel decrease of zinc concentration in maternal mixed leucocytes, or of plasma heat-labile alkaline phosphatase activity, suggesting that there was a redistribution of zinc between plasma and tissues.
4. The results indicate that iron supplementation during pregnancy alters the disposition of zinc in the mother.