Iron Absorption and Transfer to the Fetus During Pregnancy in Normal Weight and Overweight/Obese Women and the Effects on Infants Iron Status

Overview

Overweight and obesity causes low-grade systemic inflammation, which sharply increases risk for iron deficiency. Studies in our laboratory have shown that this is mainly the result of reduced dietary iron absorption because of increased hepcidin concentrations. During pregnancy, women have a large increase in iron needs because of the expansion of maternal blood volume and fetal needs. Iron deficiency anemia in infancy can impair cognitive development. Whether maternal adiposity impairs absorption and transfer of iron to the fetus, and thereby increases risk of iron deficiency in the mother and the infant is unclear.

In obese subjects, hepcidin concentrations are increased and iron absorption is believed to be reduced, leading to iron deficiency over time. How all this will influence iron supply of the fetus in obese pregnancy has not been well investigated to date. Even if maternal and fetal iron uptakes are regulated separately, it is unclear to what extent maternal subclinical inflammation might influence this process. A small study by Dao et al. indicated that maternal-fetal iron transfer was impaired in obese pregnant women, possibly due to hepcidin up-regulation. In this study, both maternal BMI as well as hepcidin were negatively correlated with cord blood iron status. Maternal hepcidin and c-reactive protein were significantly higher and cord blood iron was significantly lower in the obese compared to the normal weight. Hepcidin was shown to have an effect on iron transfer across the placenta in the study by Young et al.: the transfer was increased in women with undetectable hepcidin at delivery compared to those with higher levels. As of now, clear associations between maternal BMI or maternal hepcidin concentration and fetal iron status were not shown.