FBC (Full Blood Count): Hb below 120g/L indicates anaemia. There is often a low MCV (microcytic), low MCH (hypochromic) anaemia with iron deficiency, although microcytic hypochromic anaemia can also indicate haemoglobinopathies.
This is the first laboratory test to become abnormal in iron deficiency and is the most useful and easily available parameter for assessing iron deficiency (<30 mcg/L). Other tests like serum iron, or total iron binding, lack sensitivity and specificity so are not recommended in routine diagnosis.
2.4.1. All women should be given the leaflet regarding anaemia and iron deficiency in pregnancy.
2.4.2. Oral iron is the first line treatment for iron deficiency anaemia. Some women are at high risk of iron deficiency and should be offered empirical iron therapy while blood test results are awaited. (See booking flowchart). A trial of oral iron should demonstrate a rise in haemoglobin by 6 weeks.
2.4.3. Iron supplementation should be taken on alternate days. This is as effective as taking oral iron daily (Karakoc et al. 2021). It is better tolerated (fewer gastrointestinal side effects), and there will be less increase in maternal hepcidin levels, which can prevent absorption of iron from the gut.
2.4.4. Iron supplements should be taken on an empty stomach, 1 hour before meals with a source of vitamin C such as orange juice to help increase gastric absorption. Other medications or antacids (such as omeprazole), tea, or coffee should not be taken at the same time as they prevent the absorption of iron from the gut. Levothyroxine should not be taken at the same time as iron supplements, as the iron competes with the thyroxine.
2.4.5. Patients should be warned of the potential gastrointestinal side-effects associated with oral iron (abdominal pain, nausea, vomiting, diarrhoea, and dark stools).
2.4.6. Standard oral iron replacement: ferrous sulphate 200mg or ferrous gluconate 300mg on alternate days. Ferrous gluconate may have a better gastrointestinal side effect profile so be better tolerated.