The effects of oral iron supplementation on zinc and magnesium levels during pregnancy.

Serial changes in serum zinc and magnesium concentrations have been studied before conception, throughout pregnancy and at 12 weeks postpartum in 15 normal healthy women not receiving iron supplementation, 10 women receiving iron supplementation but otherwise having healthy pregnancies and five insulin-dependent diabetics who also received oral iron. Relative to pre-pregnancy values zinc concentrations progressively decreased throughout pregnancy reaching a nadir at 36 weeks gestation followed by an increase; pre-pregnancy values were achieved by 12 weeks postpartum. Magnesium concentrations also decreased throughout pregnancy reaching a nadir at 32 weeks gestation increasing thereafter again with pre-pregnancy values achieved by 12 weeks postpartum. Iron supplementation in non-diabetic and diabetic women had no significant effect upon the changes in serum concentration of either zinc or magnesium. These results suggest that the decrease in the concentrations of both elements is a normal physiological adjustment to pregnancy and that iron supplementation does not influence these changes.