Sickle cell blood transfusion. Pregnant female patient with sickle cell anaemia undergoing a blood transfusion. Gloved hands are injecting the blood from a syringe through a cannula into a vein in her arm. Sickle cell anaemia is an inherited blood disease occurring primarily in black people. It is caused by abnormal haemoglobin in oxygen- carrying red blood cells, which makes the cells sickle-shaped. Blood transfusions may be performed to temporarily replace these deformed red blood cells. This may be done regularly for people who suffer frequent and severe sickle cell crises. It is also vital during pregnancy, when red blood cells supply oxygen to the growing foetus as well.