Anemia

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Anemia

Plasma volume increases 50% during pregnancy, while red cell volume increases 25%, causing lower hemoglobin and hematocrit values, which are maximally changed around the 24th to 28th weeks. Anemia in pregnancy is often defined as a hemoglobin measurement below 10 g/dL or hematocrit below 30%. Anemia is very common in pregnancy, causing fatigue, anorexia, dyspnea, and edema. Prevention through optimal nutrition and iron and folic acid supplementation is desirable. 

A. Iron Deficiency Anemia
Many women enter pregnancy with low iron stores resulting from heavy menstrual periods, previous pregnancies, breast feeding, or poor nutrition. It is difficult to meet the increased requirement for iron through diet, and anemia often develops unless iron supplements are given. Red cells may not become hypochromic and microcytic until the hematocrit has fallen significantly. When this occurs, a serum iron level below 40 ug/dL and a transferrin saturation less than 10% suggest iron deficiency anemia. Treatment consists of a diet containing iron-rich foods and 60 mg of elemental iron (eg, 300 mg of ferrous sulfate) three times a day with meals. Iron is best absorbed if taken with a source of vitamin C (raw fruits and vegetables, lightly cooked greens). All pregnant women should take daily iron supplements.

B. Folic Acid Deficiency Anemia
Folic acid deficiency anemia is the main cause of macrocytic anemia in pregnancy, since vitamin B12 deficiency anemia is rare in the childbearing years. The daily requirement of folic acid doubles from 0.4 mg to 0.8 mg in pregnancy. Twin pregnancies, infections, malabsorption, and use of anticonvulsant drugs such as phenytoin can precipitate folic acid deficiency. The anemia may first be seen in the puerperium owing to the increased need for folate during lactation.

The diagnosis is made by finding macrocytic red cells and hypersegmented neutrophils in a blood smear. However, blood smears in pregnancy may be difficult to interpret, since they frequently show iron deficiency changes as well. Because the deficiency is hard to diagnose and folate intake is inadequate in some socioeconomic groups, 0.8-1 mg of folic acid is given as a supplement in pregnancy; the dose in established deficiency is 1-5 mg/d.

Good sources of folate in food are leafy green vegetables, orange juice, peanuts, and beans. Cooking and storage of food destroy folic acid. Strict vegetarians who eat no eggs or milk products should take vitamin B12 supplements during pregnancy and lactation.

C. Sickle Cell Anemia
Women with sickle cell anemia are subject to serious complications in pregnancy. The anemia becomes more severe, and crises may occur more frequently. Complications include infections, bone pain, pulmonary infarction, congestive heart failure, and preeclampsia. There is an increased rate of spontaneous abortion and higher maternal and perinatal mortality rates. Intensive medical treatment may improve the outcome for mother and fetus. Frequent indicated transfusions of packed cells or leukocyte-poor washed red cells lower the level of hemoglobin S and elevate the level of hemoglobin A; this minimizes the severity of anemia and the risk of sickle cell crises.

Genetic counseling should be offered to patients with sickle cell disease or sickle trait. They may wish to undergo first-trimester chorionic villus biopsy or second-trimester amniocentesis to determine whether the abnormality has been passed on to the fetus. IUDs and oral contraceptives are relatively contraindicated, but progestin-only contraceptives may be used. Women with sickle cell trait alone usually have an uncomplicated gestation except for an increased risk of urinary tract infection. Sickle cell-hemoglobin C disease in pregnancy is similar to sickle cell anemia and is treated similarly.

Allen LH: Anemia and iron deficiency: effects on pregnancy outcome. Am J Clin Nutr 2000;71(5 Suppl):1280S.

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