Early signs of maternal iron deficiency do not influence the iron status of the newborn, but are associated with higher infant birthweight

Objective . To investigate the associations between maternal iron status, pregnancy outcome and newborn iron status using sensitive and specific red blood cell indices reflecting iron‐deficient erythropoiesis. Design and setting . Cross‐sectional study in Kuopio University Hospital, Finland. Population . One hundred and ninety‐two pregnant women and their full‐term newborns (cord blood). Methods . Quartile analysis and Spearman correlations were used to investigate the associations of the iron status of pregnant women with that of their newborns, and with pregnancy outcome. Main outcome measures. Maternal and cord blood analysis including indices reflecting the hemoglobin (Hb) content of red blood cells as well as serum iron, transferrin saturation, transferrin receptor and ferritin. Gestational age, birthweight and placental weight. Results. The highest quartile of the maternal percentage of hypochromic red blood cells (%HYPOm) indicating the lowest iron status was associated with a high birthweight and a long duration of pregnancy. The newborns in this group did not show any signs of iron deficiency even though the maternal %HYPOm was elevated. Conclusions. In a well‐nourished maternal population, lower maternal iron status did not affect the iron accumulation on the fetal side. However, longer duration of pregnancy and growth of the fetus appeared to be associated with a lower amount of iron for Hb synthesis in maternal red blood cells, as reflected by the increased maternal %HYPOm, birthweight and length of gestation.