Anemia is a disorder in which there are too few red blood cells in the blood.
Normally, the bone marrow does not produce new red blood cells between birth and 3 or 4 weeks of age, causing a slow drop in the red blood cell count (called physiologic anemia) over the first 2 to 3 months of life. Very premature newborns have a slightly greater drop in red blood cell count. More severe anemia can occur when
More than one of these processes can occur at the same time.
Severe red blood cell breakdown results in anemia and high levels of bilirubin in the blood (hyperbilirubinemia). Hemolytic disease of the newborn may cause the newborn's red blood cells to be destroyed rapidly. The red blood cells may also be rapidly destroyed if the newborn has a hereditary abnormality of the red blood cells. An example is hereditary spherocytosis, in which the red blood cells look like small spheres when viewed under a microscope. Another rare example occurs in some infants who lack a specific red blood cell enzyme (glucose-6-phosphate dehydrogenase [G6PD]). In these infants, exposure of the mother and fetus to certain drugs used during pregnancy (such as aniline dyes, sulfa drugs, and many others) may result in rapid breakdown of red blood cells.
Infections acquired before birth, such as toxoplasmosis, rubella, cytomegalovirus infection, herpes simplex virus infection, or syphilis, may also rapidly destroy red blood cells, as can bacterial infections of the newborn acquired during or after birth.
Blood loss is another cause of anemia. Blood loss can occur in many ways. For example, blood is lost if there is a large transfusion of fetal blood across the placenta (the organ that connects the fetus to the uterus and provides nourishment to the fetus) and into the mother's circulation (fetal–maternal transfusion) or if too much blood gets trapped in the placenta at delivery, when the newborn is held above the mother's abdomen when the umbilical cord is clamped. Twin-to-twin transfusions, in which blood flows from one fetus to the other, can cause anemia in one twin and too much blood (polycythemia) in the other twin. The placenta may separate from the uterine wall before delivery (placental abruption), leading to hemorrhage of fetal blood.
Rarely, failure of the fetal bone marrow to produce red blood cells may result in anemia. Examples of this lack of production include rare genetic disorders such as Fanconi's anemia and Diamond-Blackfan anemia. Some infections (such as cytomegalovirus infection, syphilis, and HIV) also prevent the bone marrow from producing red blood cells.
Symptoms and Diagnosis
Most infants with mild or moderate anemia have no symptoms. Moderate anemia may result in sluggishness (lethargy), poor feeding, or no symptoms. Newborns who have suddenly lost a large amount of blood during labor or delivery may be in shock and appear pale and have a rapid heart rate and low blood pressure, along with rapid, shallow breathing. When the anemia is a result of rapid breakdown of red blood cells, there is also an increased production of bilirubin, and the newborn's skin and whites of the eyes appear yellow (jaundice). Diagnosis is based on symptoms and is confirmed with blood tests.
Most infants have mild anemia and do not require any treatment.
Newborns who have rapidly lost large amounts of blood, often during labor and delivery, are treated with intravenous fluids followed by a blood transfusion. Very severe anemia caused by hemolytic disease may also require a blood transfusion, but the anemia is more often treated with an exchange blood transfusion, which lowers the bilirubin level as well as increases the red blood cell count. In an exchange transfusion, a small amount of the newborn's blood is gradually removed (one syringe at a time) and replaced with equal volumes of fresh donor blood.
Last full review/revision February 2009 by Arthur E. Kopelman, MD