The assessment of newborn iron stores at birth: a review of the literature and standards for ferritin concentrations

Abstract

Background: Serum ferritin measurements are used in clinical populations to estimate total body iron stores and the risk of subsequent iron deficiency or overload. The lack of normative newborn serum ferritin concentration data between 23 and 41 weeks has led to difficulty in establishing the incidence and degree of abnormal iron status in the neonatal period.

Objectives: The primary objective of this review was to summarize the maternal and gestational factors that determine ferritin concentrations in full-term and pre-term newborn infants and to generate comprehensive reference values. The secondary objective was to assess serum ferritin concentrations in newborn infants at risk for abnormal fetal iron metabolism, including maternal diabetes mellitus, intrauterine growth restriction and maternal smoking during pregnancy.

Methods: Serum ferritin and gestational age data at birth from 457 low-risk pre-term and term infants of 23-41 weeks gestation obtained from 35 published studies reviewed from a period of 25 years and from recently collected data from our centers were assessed by regression analysis. Slopes and intercepts of the high-risk groups were compared with the standard curve.

Results: Umbilical cord serum ferritin concentrations increased with advancing gestational age, from a mean of 63 mug/l at 23 weeks to 171 mug/l at 41 weeks gestation (p < 0.001). The infants of diabetic mothers had a lower intercept than the control infants (p < 0.001).

Conclusions: Iron deficiency and overload have been implicated in neurodevelopmental impairments. Normative cord serum ferritin data may permit a more precise assessment of infants who are at risk for abnormal iron status at birth.

Fig. 1

Ferritin concentrations as a function of gestational age in infants from the combined control data sets. The regression line and its 5th and 95th percentile confidence limits for the mean regression are shown (n = 245, r = 0.30, r² = 0.09, Y = 6.01X – 74.56; p < 0.001).

Fig. 2

The regression lines for infants of mothers who smoke (n = 19, r = 0.44, r² = 0.13, Y = 8.26X – 194.02; p = NS), infants of diabetic mothers (IDM, n = 70, r = 0.22, r² = 0.05, Y = 5.65X – 124.00; p = NS), and infants with IUGR (n = 33, r = 0.42, r² = 0.18, Y = 9.43X – 195.67; p < 0.01) in comparison with the combined control group.