Concentration of serum ferritin was analyzed in cord blood samples of 34 preterm and 24 full-term subjects, 10 fetuses which were aborted by laparotomy at 14-20 weeks of gestation, and 20 pairs of twins. The findings indicated that the fetal amount of storage iron gradually increases as the gestational age increases, it is similar in singletons and twins, within the pairs of twins, and slightly lower in some small-for-dates newborns. There was no correlation between fetal ferritin and maternal iron status. Our data suggest that the accumulation of fetal iron stores is not regulated by the fetus itself, or by maternal iron metabolism. Thus, we speculate that the placenta may have a role in this regulation.