Neonatology
Anemia of Prematurity and Blood Transfusions
Anemia of Prematurity
When an infant is born prematurely,
before approximately 34 weeks gestation, the production
of red blood cells by the bone marrow will decrease.
The reasons for this are not well understood.
Since blood cells live for only a certain number
of days, those cells which break down normally
may not be replaced at an adequate rate by the
premature bone marrow. This results in a steady
decline in the red blood cell count (hematocrit).
This drop in red blood cell count is termed 'anemia
of prematurity', and is normal and expected in
premature infants. In addition to this normal
reduction in blood cells, premature infants require
blood tests. Although very small amounts of blood
are used for blood tests, the quantities can result
in a further decrease in the
red blood cell count.
Other conditions can cause anemia as well, even
in full term infants. Blood can be lost prior
to, or at, delivery, or a process may be present
which causes an increase in the rate at which
red blood cells are broken down.
Blood Transfusions
Red blood cells carry oxygen from the lungs to
the body tissues. If the blood count falls too
far, then not enough oxygen may be delivered to
the tissues, and a blood
transfusion may be required to increase the
amount of oxygen that the blood can carry.
Infants who are sick on ventilators,
or who otherwise require extra oxygen, may need
their blood counts to be maintained at higher
levels. For this reason, very small premature
infants may require multiple transfusions, whereas
premature babies born at a later gestation may
need fewer transfusions, or none at all.
If a baby requires a transfusion, the blood will
be obtained from the blood bank. All blood in
the blood bank is tested very carefully for the
presence of hepatitis viruses and HIV. All blood
given to patients has tested negative for these
viruses. The chance of a patient acquiring any
one of these diseases from a blood transfusion
is extremely remote.
Parents may choose to locate their own blood
donor for their infant. This is called the 'directed
donor' option. Since the directed donor must have
a blood type that matches that of the infant,
a number of people may need to be screened before
a suitable donor can be found. In addition, all
blood from directed donors is tested for hepatitis
and HIV, a process which takes time.
Blood from directed donors may take a few days
to process, whereas other blood from the blood
bank has already been tested and is available
immediately. For small premature infants, there
is not usually enough time between birth and the
first transfusion to allow for blood to be obtained
from a directed donor. Since an infant's blood
type is not known prior to delivery, blood cannot
be donated before a baby is born.
As a baby reaches 34 to 36 weeks corrected age,
the bone marrow will start to produce red blood
cells again in quantities that can maintain or
increase the blood count, so transfusions may
no longer be necessary.
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