Iron deficiency - the world’s commonest nutritional disorder - affects over 2 billion people. Women and children are at greatest risk. No RCTs have assessed the effects of treatment on fetal growth (measured as birthweight for gestational age) and child development. Oral iron may increase maternal IL-6 concentration, upregulating hepcidin activity, downregulating ferroportin and trapping iron in enterocytes, hepatocytes and macrophages, leading to hypoferraemia and potentially influencing risk of preterm birth. Oral lactoferrin may reduce these effects. Although IV iron is increasingly used, no RCTs have tested its effects on maternal IL-6 concentration, fetal growth or child development. The NHMRC LEAP1 trial will compare oral iron and oral lactoferrin in women with or at risk of iron deficiency anaemia who present in the second trimester. Women will be randomly assigned to 80 mg oral elemental iron daily or 200 mg oral lactoferrin, in identical capsules in a blinded two arm study. IV iron will be reserved for women who do not respond by 36 weeks gestation. The co-primary outcomes are (i) fetal growth (birth weight for gestational age) and the proportion of women who receive IV iron infusion by standard protocol or whose Hb closest to delivery (but after 34 weeks gestation) is less than 110 g/L. All are welcome to learn more about this important first step in answering the question “Is oral lactoferrin more effective and better tolerated in treating iron deficiency anaemia in pregnancy than oral iron?”