Neutropenia is an abnormally low number of white blood cells. These cells, which are called neutrophils, help the body fight infection. This article discusses neutropenia in newborns.

White blood cells are produced in the bone marrow. They are released into the bloodstream, and travel wherever they are needed. Low levels of neutrophils occur when the bone marrow cannot replace them as fast as needed.

In babies, the most common cause is infection. A very severe infection may cause neutrophils to be used up quickly, and may also prevent the bone marrow from producing more neutrophils.

Sometimes, an infant who is not sick will have a low neutrophil count for no obvious reason. Some disorders in the pregnant mother, such as preeclampsia, can also lead to neutropenia in infants.

In rare cases, mothers may have antibodies against their baby's neutrophils. These antibodies cross the placenta before birth and cause the baby's cells to break down (alloimmune neutropenia). In other rare cases, a problem with the baby's bone marrow may lead to decreased white blood cell production.

A small sample of the baby's blood will be sent to the laboratory for a complete blood count (CBC) and blood differential. A CBC reveals the number and type of cells in the blood. The differential helps determine the number of different types of white blood cells in a blood sample.

The source of any infection should be found and treated.

In many cases, neutropenia goes away on its own as the bone marrow recovers and begins to produce enough white blood cells.

In rare cases when the neutrophil count is low enough to be life threatening, the following treatments may be recommended:

• Medicines to stimulate white blood cell production
• Antibodies from donated blood samples (intravenous immune globulin)

The baby's outlook depends on the cause of the neutropenia. Some infections and other conditions in newborns can be life threatening. However, most infections usually do not cause long-term side effects after the neutropenia goes away or is treated.

Alloimmune neutropenia will also get better once the mother's antibodies are out of the baby's bloodstream.