Haema 2013; 4(1):90-99
by Theoni Leonidopoulou
Hematology Clinic, Sismanogleio General Hospital, Athens, Greece
Abstract
Anemia is the most common complication of pregnancy. Pregnancy is associated with nor- mal physiological changes that assist fetal development and prepares the mother for delivery. The greater increase in plasma volume than in red cell mass results in a dilutional anemia. Physiological or dilutional anemia of pregnancy is seen in most women and is often normochromic and normocytic. Pathological anemias are also common. They are almost always related to nutritional deficiencies, particularly iron deficiency or folic acid deficiency. Minor causes of anemia are vitamin B12 deficiency, pregnancy associated complications, such as sepsis, preeclampsia, hemoglobinopathies, hemolytic anemia, aplasia. The WHO defines anemia in pregnancy as an hemoglobin value below 11g/dl at any point during pregnancy. The Centers for Disease Control has defined anemia in pregnancy as hemoglobin levels less than 11g/dl in the first and third trimesters or less than 10,5 g/dl in the second trimester. Women with values less than these are considersd to have a pathological anemia. Of all anemias diagnosed in pregnancy, 75% are due to iron deficiency. Iron deficiency anemia (IDA) is associated with increased maternal and perinatal morbidity and mortality and long term adverse effects in the newborn. Requirements for absorbed iron increase during pregnancy and dietary measures are inadequate to reduce the frequency of IDA. Oral iron supplements from early pregnancy to delivery, efficiently prevent IDA. Folic acid deficiency is the second most common cause of anemia in pregnancy after iron deficiency. Periconceptual folic acid is advised to reduce the incidence of neural tube defects. It should be continued throughout at least the first trimester. Folate prophylaxis should be considered in at risk groups such as those on anticonvulsants and with chronic hereditary or acquired red cell disorders. Deficiency of vitamin B12 is rare in pregnancy. Maternal cobalamin stores are about 3000μg, more than adequate for the developing fetus whose requirement is around 50 μg. During late pregnancy, B12 levels fall as a result of hemodilution and hormonal changes. After delivery levels return rapidly to normal without supplementation. Other disorders, such as hemoglobinopathies, also contribute to the high prevalence of anemia world- wide. Problems of pregnancy are nearly always restricted to sickle cell disorders and the thalassemias. Pregnancy in heterozygotes for any of these conditions is usually not accompanied by complications. In the management of hemoglobinopathies, it is important to identify women who require special management or prophylaxis to overcome the extra hematological stress of pregnancy and couples whose offspring are at risk of serious hemoglobinopathy. Autoimmune disorders are common in young women. The antibodies can cross the placenta and cause hemolysis in the fetus. Steroids are usually effective in controlling IgG mediated hemolysis presenting in pregnancy. Aplastic anemia may develop during pregnancy and sometimes improves spontaneously after delivery.