Pregnant women normally experience mild physiological anaemia because their blood volume increases faster than the rise in the number of red blood cells in their circulation. Iron is required for the production of haemoglobin, the oxygen-carrying substance in red blood cells. If a woman doesn’t have enough iron in her body, she won’t be able to make enough red blood cells, so her anaemia could become serious. Eating a diet containing plenty of iron-rich foods, or taking iron tablets, helps her to make enough red blood cells to carry the oxygen she and her growing fetus need.