Abstract
EDITOR,—Philip Steer and colleagues studied the relation between maternal haemoglobin concentration in pregnancy and birth weight and suggested that their results show that low haemoglobin concentrations are advantageous in improving fetal growth.1 They even suggested a theoretical risk that treatment to improve haemoglobin concentrations may be detrimental to the fetus. They do not discuss the alternative explanation that lower haemoglobin concentrations are the result …