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FETAL ANEMIA

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Anemia continues to be an uncommon, but life-threatening, condition to the developing fetus. Red cell alloimmunization has historically been the most common cause of fetal anemia in the United States and in many other parts of the world. Alternative causes of fetal anemia include parvovirus infection and other less common conditions.

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DEFINITION OF FETAL ANEMIA

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Fetal anemia is defined as a hemoglobin value below 2 standard deviations from the mean. The fetal hemoglobin increases with advancing gestation (Table 13-1). Reference ranges for fetal hemoglobin have been established using umbilical blood sampling.1,2

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Table Graphic Jump Location
Table 13-1REFERENCE RANGES FOR FETAL HEMOGLOBIN CONCENTRATIONS (G/DL) AS A FUNCTION OF GESTATIONAL AGE2
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Fetal anemia is categorized as mild, moderate, and severe, based on the degree of deviation from the median for gestational age. Severe anemia may cause hydrops and fetal demise.2

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MOST COMMON CAUSES OF FETAL ANEMIA

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Fetal anemia can result from a large number of pathologic processes (Table 13-2). The most common causes in the United States are maternal alloimmunization and parvovirus infection.3 Other causes include inherited conditions such as alpha-thalassemia, and genetic metabolic disorders, as well as acquired conditions, such as fetal blood loss and infection. Fetal anemia can occur in association with Down syndrome, due to transient abnormal myelopoeisis (TAM), a leukemic condition that occurs in about 10% of infants with Down syndrome.4 Vascular tumors and arteriovenous malformations of the fetus or placenta are also rare ...

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