Iron deficiency anaemia

What it is

Iron deficiency anemia is a hypochromic microcytic anemia. In the workup of anemia by cell size it belongs to the microcytic group under defective heme synthesis, where it is listed as iron deficiency (late) together with lead poisoning, sideroblastic anemia and anemia of chronic disease, while the thalassemias sit in the same group under defective globin chain.

Causes and risk

Menorrhagia is one route in. Pregnancy is another, because in pregnancy iron absorption is low. In pregnancy the hemoglobin that is called iron deficiency anemia is set by trimester: under 11.0 g/dl in the 1st trimester, under 10.5 g/dl in the 2nd and 3rd trimester, allowing for physiological dilution, and under 10.0 g/dl in the postpartum period. The 3rd trimester line is not the same on every page: it is given as under 10.5 g/dl alongside the 2nd trimester in one source, and as under 11 g/dL alongside the 1st trimester in another, so that under 10.5 g/dL there belongs to the 2nd trimester alone. The causes group three ways: increased demand, that is pregnancy, lactation and growing age; poor intake, that is achlorhydria, which is reduced acid in the stomach and so reduced absorption, baby milk, and malabsorption; and increased loss, GI and GU. The risk factors named are poor dietary intake, frequent pregnancies with short interpregnancy intervals, heavy menstrual bleeding before pregnancy, and chronic illnesses such as inflammatory bowel disease. The required daily allowance of iron is 8 mg/d for a male or female over 50 y/o and 18 mg/d for a female during reproductive age. In pregnancy the total requirement is 1000-1100 mg: 25 mg/day in early pregnancy, 30 mg/day at 20-32 week and 25 mg/day at 32-40 week. It goes to the RBC, 500 mg, to the fetus and placenta, 450 mg, and to blood loss, 200 mg. Fetal iron needs are satisfied at the expense of the mother need and are greater in the later stage of pregnancy, and there is a poor relationship between maternal and fetal serum iron.