Page 2466 - Hematology_ Basic Principles and Practice ( PDFDrive )

C H A P T E R 151

HEMATOLOGIC CHANGES IN PREGNANCY

Caroline Cromwell and Michael Paidas

Hematologic conditions are often seen during pregnancy. These range similar to those in nonpregnant patients. Anemia and low ferritin
from the simple to the complex. The primary physiologic hematologic levels are considered diagnostic.
1
changes during pregnancy relate to the expansion of plasma volume. Because the typical diet in the United States provides only 50%
In addition to physiologic changes of pregnancy, a prothrombotic of daily iron requirements for pregnant women and because of the
state develops as the pregnancy advances that is thought to prepare relatively high prevalence of iron deficiency among women of child-
2
the mother and fetus for eventual placental separation. All require bearing age, routine iron supplementation in pregnancy is recom-
14
proper planning, anticipation, and discussion with the treating physi- mended. Currently, the Centers for Disease Control and Prevention,
cians as well as the patient. The effect of the condition on the the American Dietetic Association, and the American College of
pregnancy, and conversely the effect of the pregnancy on the condi- Obstetrics and Gynecology recommend 15 to 30 mg/day of elemen-
tion, should be considered. The evolving clinical picture as the tal iron to prevent adverse outcomes from iron-deficiency anemia. 14–18
pregnancy progresses must also be taken into account. Multidisci- Treatment should be from the beginning of gestation to 3 months
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plinary planning and communication are essential. postpartum. On the basis of results of a study by Casanueva et al,
Anemia and thrombocytopenia are common hematologic condi- weekly therapy with 120 mg of iron appears to be a safe and effective
tions seen for a variety of reasons during pregnancy and are addressed alternative to daily therapy. The side effects associated with iron
in this chapter. Inherited and acquired bleeding disorders affect therapy—constipation, diarrhea, nausea—are well known.
pregnant women, and coagulation parameters must be monitored Intravenous iron is appropriate in certain circumstances; evidence
during pregnancy and delivery. Venous thromboembolism (VTE) from a recently published randomized trial by Al et al supports the
during pregnancy remains a high-morbidity, high-risk situation use of intravenous iron therapy to replenish iron stores in appropri-
that is challenging for clinicians. These more common hematologic ately selected patients, including those who have not tolerated a trial
problems and dilemmas in management are discussed in this of oral iron therapy and those with severe iron deficiency. 20
chapter. Multiple studies have shown that routine iron supplementation
in pregnancy decreases the incidence of iron-deficiency anemia. In a
randomized, double-blind study in which 275 iron-replete pregnant
ANEMIA IN PREGNANCY women received either a daily iron supplement or placebo from the
time of enrollment (all women were enrolled before week 20) to 28
Anemia in pregnancy affects approximately half of all pregnancies weeks of gestation, the incidence of both low-birth-weight and
worldwide. It is more prevalent in underdeveloped countries. preterm low-birth-weight infants was lower among women who
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The World Health Organization classifies anemia in pregnancy as received daily iron. Nonetheless, there are limits to the effectiveness
hemoglobin below 11 g/dL, although in developing countries it is of routine iron supplementation. After all, the recommendation by
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clinically defined as hemoglobin below 10 g/dL. Physiologic anemia prominent public health organizations for universal iron supplemen-
occurs during pregnancy as the blood volume increases to a greater tation has not led to a commensurate decrease in the incidence of
proportion than the red blood cell (RBC) mass, resulting in a dilu- iron-deficiency anemia in pregnancy 22,23 or an increase in maternal
tional anemia. Total circulatory volumes increase by approximately hemoglobin levels. 24,25 Compliance is an important factor in this
50% greater than the prepregnancy volume. Plasma volume and RBC discussion. A large, multicenter, randomized, controlled trial on the
mass return to baseline during the first and second postpartum benefits of iron supplementation during pregnancy in the United
months. Common maternal signs of anemia include pallor, tachy- States is needed to draw more definitive conclusions.
pnea, fatigue, and headache. Hemoglobin levels less than 6 g/dL in
pregnant women can be associated with significant maternal and fetal
complications. At these levels, tissue oxygenation decreases and may Other Nutritional Deficiencies
2–4
lead to high-output congestive heart failure in the mother. Multiple
studies have shown a correlation between maternal anemia and Folate deficiency and, less commonly, vitamin B 12 deficiency are the
increased rates of both preterm (<37 weeks of gestation) and low- next most common causes of anemia in pregnancy. Cobalamin and
birth-weight deliveries. 5–13 There are varied etiologies behind anemia folate are critical for fetal growth because they are necessary for the
in pregnancy. production of tetrahydrofolate. Tetrahydrofolate is key in the DNA
synthesis pathway.
Folate deficiency accounts for 95% of megaloblastic anemias in
Iron-Deficiency Anemia pregnancy. Folate deficiency complicates between 1% and 4% of
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pregnancies in the United States and affects approximately one-third
27
Iron-deficiency anemia is the most common cause of anemia in of pregnancies worldwide. Similar to iron-deficiency anemia, the
pregnancy. It has been identified as a risk factor for preterm delivery incidence of megaloblastic anemia in pregnancy is increased in ado-
and low birth weight. Iron requirements increase during pregnancy lescents, women of low socioeconomic status, and women with
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because of maternal and fetal erythropoiesis. Generally, hemoglobin multiple closely spaced births. The folic acid requirement for
levels decrease throughout pregnancy and then may increase during nonpregnant women is 50 to 100 µg/day, but this increases to 150 µg
the last month of pregnancy. Ferritin levels also increase in the last during pregnancy as RBC mass in the mother increases and as fetal
month of pregnancy because it is an acute-phase reactant. Erythro- demands for folate grow with cell proliferation. 29
poietin levels increase throughout pregnancy. The clinical symptoms Diagnosis of folate deficiency is best based on RBC folate levels.
of iron deficiency are similar to those in nonpregnant patients and An elevated homocysteine level also helps confirm the diagnosis.
include fatigue, pallor, tachycardia, and poor exercise tolerance. The Pregnant women should at least receive 400 µg of folic acid per day.
diagnosis and treatment of iron-deficiency anemia are generally Vitamin B 12 deficiency is much less common during pregnancy.

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