Anemia in the Newborn

ByAndrew W. Walter, MS, MD, Sidney Kimmel Medical College at Thomas Jefferson University
Reviewed/Revised Nov 2022

Anemia is a disorder in which there are too few red blood cells in the blood.

  • Anemia can occur when red blood cells are broken down too rapidly, too much blood is lost, or the bone marrow does not produce enough red blood cells.

  • If red blood cells are broken down too rapidly, anemia may develop and levels of bilirubin (a yellow pigment produced during the normal breakdown of red blood cells) increase, and the newborn’s skin and the whites of the eyes can appear yellow (a condition called jaundice).

  • If a large amount of blood is lost very rapidly, the newborn may become seriously ill and develop shock, appear pale, have a rapid heart rate, and have low blood pressure along with rapid, shallow breathing.

  • If there is less severe blood loss, or the blood is lost gradually, the newborn may appear normal but pale.

  • Treatment may involve fluids given by vein (intravenously) followed by a blood transfusion or an exchange transfusion.

Red blood cells contain hemoglobin, a protein that gives blood its red color and enables it to carry oxygen from the lungs and deliver it to all body tissues. Oxygen is used by cells to help produce from food the energy that the body needs, leaving carbon dioxide as a waste product. Red blood cells carry carbon dioxide away from the tissues and back to the lungs. When the number of red blood cells is too low, blood carries less oxygen, and fatigue and weakness develop (see also Overview of Anemia in adults.)

Bone marrow contains specialized cells that produce blood cells. Normally, the bone marrow produces very few 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 greater drop in red blood cell count. This condition is called anemia of prematurity. Anemia of prematurity most commonly affects infants whose gestational age (length of time spent in the uterus after the egg is fertilized) is less than 32 weeks and infants who have spent many days in the hospital.

More severe anemia can occur when

  • Red blood cells are broken down too rapidly (a process called hemolysis).

  • A lot of blood is taken from premature newborns for blood tests.

  • Too much blood is lost during labor or delivery.

  • The bone marrow does not produce enough new red blood cells.

More than one of these processes can occur at the same time.

Rapid breakdown of red blood cells (hemolysis)

Severe red blood cell breakdown results in anemia and high levels of bilirubin in the blood (hyperbilirubinemia).

Hemolytic disease of the newborn is a condition that may cause the newborn’s red blood cells to be destroyed rapidly by antibodies from the mother's blood.

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 example occurs in infants who lack a red blood cell enzyme called glucose-6-phosphate dehydrogenase (G6PD deficiency). 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.

Hemolysis may also occur with hemoglobinopathies. Hemoglobinopathies are genetic disorders that affect the structure or production of hemoglobin. Hemoglobin is a protein inside red blood cells that enables the cells to carry oxygen from the lungs and deliver it to all parts of the body. Thalassemia is an example of a hemoglobinopathy that can rarely cause problems in newborns.

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

Blood loss is another cause of anemia. Blood loss in a newborn can occur in many ways. For example, blood is lost if there is a large movement of the fetus's blood across the placenta (the organ that connects the fetus to the uterus and provides nourishment to the fetus) and into the mother's blood circulation (called fetal-maternal transfusion). Blood can also be lost if too much blood gets trapped in the placenta at delivery, which can happen when the newborn is held above the mother’s abdomen for too long before 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 uterus before delivery (placental abruption), or the placenta may be attached in the wrong place (placenta previa), leading to loss of blood in the fetus.

Blood loss may occur when certain invasive procedures are done to the fetus to detect gene and chromosome abnormalities. Invasive procedures are those that require insertion of an instrument into the mother's body. These procedures include amniocentesis, chorionic villus sampling, and umbilical blood sampling.

Sometimes blood loss occurs when the newborn is injured during delivery. For example, rupture of the liver or spleen during delivery may cause internal bleeding. Rarely, bleeding can occur under the newborn's scalp when a vacuum extractor or forceps is used during delivery.

Blood loss can also occur in newborns who have a deficiency of vitamin K. Vitamin K is a substance that helps the body form blood clots and helps control bleeding. Vitamin K deficiency can cause hemorrhagic disease of the newborn, which is characterized by a tendency to bleed. Newborns normally have low levels of vitamin K at birth. To prevent bleeding, newborns are routinely given an injection of vitamin K at birth.

Internal bleeding that leads to anemia can occur in babies who are born with a severe, inherited bleeding disorder such as hemophilia, especially with a difficult delivery.

Frequently drawing a sick newborn's blood may also contribute to anemia.

Decreased red blood cell production

Before birth, the fetus's bone marrow may fail to produce enough new red blood cells. This rare defect may result in severe anemia. Examples of this lack of production include rare genetic disorders such as Fanconi syndrome and Diamond-Blackfan anemia.

After birth, some infections (such as cytomegalovirus infection, syphilis, and human immunodeficiency virus [HIV]) may also prevent the bone marrow from producing enough red blood cells. Rarely, newborns may also be lacking certain nutrients, such as iron, folate, which may cause anemia because the bone marrow is then unable to produce red blood cells.

Symptoms of Anemia in the Newborn

Most infants with mild or moderate anemia have no symptoms. Moderate anemia may result in sluggishness (lethargy) or poor feeding.

Complications of anemia in newborns

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 may appear yellow (jaundice).

Diagnosis of Anemia in the Newborn

  • Before birth, prenatal ultrasound

  • After birth, symptoms and blood tests

Before birth, doctors may do a prenatal ultrasound and may sometimes see signs of anemia in the fetus.

After birth, the diagnosis of anemia is based on symptoms and is confirmed with tests done on a sample of the newborn's blood. Additionally, in some states of the United States, newborns are screened for some of the causes of anemia, such as G6PD deficiency.

Lab Test

Treatment of Anemia in the Newborn

  • For anemia caused by rapid blood loss, fluids by vein and a blood transfusion

  • For anemia caused by hemolytic disease, treatment varies

  • Sometimes iron supplements

Most healthy premature 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 fluids given by vein (intravenously) 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 transfusion, which both lowers the bilirubin level and increases the red blood cell count. In an exchange transfusion, a small amount of the newborn’s blood is gradually removed and replaced with equal volumes of fresh donor blood.

Some infants are given liquid iron supplements to help them increase their red blood cell count faster.

Newborns who have jaundice may be treated with phototherapy or "bili lights", which help lower the bilirubin level.

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