Iron absorption during normal human pregnancy: a study using stable isotopes

Abstract

The absorption of iron has been determined in nine healthy women studied serially during pregnancy and once post delivery. Following the oral administration of 5 mg aqueous54FeSO4plus ascorbic acid and the intravenous injection of 200 μg57FeSO4, the isotope ratios of54Fe:56Fe and57Fe:56Fe in serum were measured by the use of inductively-coupled-plasma mass spectrometry whereby metal ions are vaporized into an argon plasma without previous blood sample preparation. Mean oral Fe absorption was 7.6 (range 1–22) % at 12 weeks gestation, 21.1 (range 9–58) % at 24 weeks, 37.4 (range 18–56) % at 36 weeks and 26.3 (range 8–54) % at 12 weeks post delivery. All the other biochemical and haematological indices were within normal limits for pregnancy. The significant increase (P< 0.01) in Fe absorption during normal pregnancy suggests that most women would have the potential to meet the Fe demands of pregnancy without the need for supplementation if dietary Fe has similar availability to the aqueous preparation.