To determine the associations of maternal hemoglobin and iron status with pregnancy outcomes.
Data were analyzed from pregnant women receiving iron-containing nutritional supplements in Ghana (n= 1,159), Malawi (n=1,067), and Bangladesh (n=979). Hemoglobin and blood biomarkers of iron status were measured in early (= 20 wk gestation) and late (34-36 wk gestation) pregnancy. The primary biomarker for iron status was soluble transferrin receptor. Additional biomarkers of iron status included zinc protoporphyrin (Ghana and Malawi) and ferritin (Bangladesh).
In early pregnancy, higher hemoglobin was associated with a longer duration of gestation in all three cohorts, and with higher birth weight and length-for-age (LAZ) in Malawi. In late pregnancy, there was a non-linear relationship of hemoglobin with duration of gestation in Ghana (but not Malawi or Bangladesh), and no association with any other birth outcome in any of the sites. Higher iron status in early pregnancy was associated with a longer duration of gestation in Malawi and Bangladesh, and higher birth weight, LAZ, and head-circumference-for-age in Malawi. In late pregnancy, higher iron status was associated with lower birth weight (Ghana and Bangladesh), lower LAZ (Ghana and Bangladesh), and smaller head circumference (Bangladesh). Higher iron status in late pregnancy was associated with a shorter duration of gestation in Bangladesh and a longer duration in Malawi.
In early pregnancy, higher hemoglobin and iron status are associated with better birth outcomes. In late pregnancy, hemoglobin generally shows no association with birth outcomes and higher iron status tends to be associated with poorer birth outcomes.