Pregnant women's absorption of iron from prenatal supplements.

A randomized, double-blind, crossover study was carried out on iron absorption from three prenatal supplements by women in the first trimester of pregnancy. The supplements were given to fasting subjects as a single pill early in the morning, and iron absorption was determined from measurements of serum iron performed during the course of the day. Iron absorption from two of the supplements was substantially less than the 3.5 mg recommended for the prevention of iron deficiency during pregnancy. The third supplement, containing reduced amounts of calcium and magnesium, provided on the average 3.6 mg of absorbed iron to the subjects. These results support previous findings in nonpregnant subjects that the availability of iron in a prenatal supplement is affected by the overall composition of the supplement.