Prenatal Iron Status and Its Association With Cord Blood and Infant Ferritin Level

Iron deficiency (ID) is the most common micronutrient deficiency globally. Pregnant women and young children are at risk of ID. During pregnancy, there is an increased demand for iron to accommodate the needs of the fetal-placental unit. This increase in physiologic demand for iron renders pregnant women vulnerable to ID. In fact, ID is the major cause of anemia in pregnancy and can increase the perinatal maternal morbidity and mortality. Iron is also an essential micronutrient for fetal and infant brain development. ID in early life is associated with worse cognitive, motor, social emotional as well as neurophysiological development. Besides neurodevelopment, iron is also essential for proper immune function affecting both innate and adaptive cell, and has implications for childhood atopic diseases.

Globally, there is an increasing trend of breastfeeding especially in developed countries.In Hong Kong, the government's continuing effort to promote breastfeeding has successfully boosted the rate of babies being breastfed. This encouraging information means more children will benefit from the many advantages of breast milk over formula milk, yet exclusive breastfeeding, particularly in the context of maternal ID and late weaning, may be a risk factor of ID in the infants. In view of the adverse impact of fetal and infant ID on neurocognitive development, it is important to evaluate the iron status of young infants, the effect of feeding practices on development of ID and the risk factors of ID in early infancy.

Maternal ID is prevalent worldwide varying from 20% to 90%. Previous investigation performed in the Department of Obstetrics and Gynaecology, Prince of Wales Hospital, concurred a significant prevalence (39%) of ID (serum ferritin < 15 microgram/L) among 100 asymptomatic pregnant women. Most fetal iron needed for infant growth is acquired in the third trimester from maternal iron store, in preparation for the high growth rate in the first 6 months of life. Iron status at birth is therefore critical and impaired iron status may persist into early childhood. However, low maternal prenatal iron levels measured as serum ferritin have not been consistently linked with low cord blood serum ferritin (CBSF) concentrations. Some studies reported that there was no correlation between serum ferritin of mothers and babies. However, others found that maternal ID or anemia, especially the severe type, adversely affected cord blood or infant iron status. Further studies are needed to evaluate how prenatal maternal iron status affects newborn's ferritin level at birth. Such data is necessary to guide future recommendations regarding the need of iron supplement in pregnant or lactating women and/or their infants. Hence, this study aimed to examine the associations between maternal prenatal ferritin levels with CBSF and to compare the ferritin levels with different feeding practices in early infancy at 3 months of age.