Iron is essential for nearly all living organisms, but iron requirements vary throughout one's lifetime. Pregnancy is a period notable for vastly increased iron requirements. Iron is needed to support maternal adaptations throughout pregnancy and to enable the growth and development of both the placenta and fetus. Insufficient iron has long been linked to adverse pregnancy outcomes; thus, universal iron supplementation is common practice before and during pregnancy. In high-income countries, however, where foods are often iron-fortified and red meat consumption is common, too much iron supplementation during pregnancy has become a concern, as iron excess has also been linked to adverse pregnancy outcomes. Advances in clinical management have enabled more women with iron-related disorders to conceive; thus, it is important to understand iron physiology and how iron disorders affect pregnant women and their offspring to help inform clinical practice and optimize outcomes. This chapter will address the physiologic iron homeostasis of pregnancy and discuss what is currently known about iron-related disease and their consequences on human pregnancy.