Maternal and infant serum ferritin concentrations across pregnancy and postpartum: a longitudinal study in Norway.

Introduction: Adequate iron status is particularly important during pregnancy and infancy, as iron deficiency can pose health risks to the woman, developing fetus, and future child. However, data in these population groups are scarce in Norway. Aim: To describe serum ferritin concentrations in a cohort of pregnant women in Norway, followed through the postpartum period, and their infants. Further, to examine associations between maternal and infant serum ferritin concentrations, and to assess the influence of dietary supplement use and breastfeeding status on serum ferritin levels. Methods: In this longitudinal cohort study, 137 pregnant women in Norway were enrolled and followed at gestational week 18 and 36, and at 3 and 6 months postpartum together with their infants. Infant and maternal serum ferritin concentrations were measured. Results: At gestational week 18, 14% of pregnant women were iron deficient (serum ferritin < 15 µg/L), and 44% had depleted iron stores (< 30 µg/L). By gestational week 36, the prevalence of iron deficiency had increased to 65% and depleted stores to 95%. Infant ferritin concentrations declined between 3 and 6 months of age. At 3 months, 96% of infants had sufficient iron status (≥ 50 µg/L). At 6 months, 90% remained sufficient, while 10% were iron deficient (< 15 µg/L). No associations were observed between iron status and dietary iron supplement use or breastfeeding status. Conclusion: A substantial proportion of the women were found to have iron deficiency, and depleted iron stores both during pregnancy and the postpartum period measured by serum ferritin concentrations. In contrast, the infants generally showed adequate iron status, and although serum ferritin levels declined between 3 and 6 months of age, the prevalence of iron deficiency remained low.