Serum zinc changes due to iron supplementation in teen-age pregnancy

Serum zinc and iron concentrations in a group of pregnant teen-agers supplemented with a multivitamin were compared during pregnancy with a group supplemented with a multivitamin containing 18 mg Fe. Serum measurements were at 13 wk of gestational age (prestudy) and during supplementation at 20, 32, and 38 wk, delivery, and 4 and 12 wk postpartum. Hematocrit measurements were used to adjust the measured metal concentrations for the diluting effect of the normal blood-volume increase. The non-Fe-group mean, adjusted serum Zn concentrations showed no change, but the serum Fe decreased to 28% below prestudy concentrations at 38 wk. In contrast, the Fe-supplementation group showed a progressive increase in Fe concentrations to a maximum of 38% above prestudy concentrations at 4 wk postpartum and a 35% decrease from prestudy Zn concentrations during the third trimester. The results of this study suggest that 18 mg Fe/d is adequate supplementation for nonanemic teen-age pregnancy and depresses the serum Zn concentration.