Anemia in the newborn

[Sommer]

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.

(See also Overview of Anemia.)
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.