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Occasionally, babies and young children can become ill because
of disorders of the body’s chemistry (inborn errors of metabolism).
Many of these disorders are treatable or preventable if detected
early. Two such conditions are phenylketonuria and thyroid deficiency,
which can be diagnosed by a simple blood test. For this reason,
all newborn babies in the UK are tested for these conditions. Within
the East Anglian Region, babies at high risk of cystic fibrosis
can also be identified using the same blood test.
How is the screening done?
The tests are performed on a few drops of the baby’s blood,
taken from a pin prick to the heel, and collected on blotting
paper. The blood is taken when the baby is 6–8 days old.
Most parents are naturally concerned about the heel prick, but
your midwife will be experienced in performing the test safely
and with minimal discomfort to your baby. Occasionally, a repeat
test is required if insufficient blood has been provided on the
first sample to complete all the tests. This is the commonest
reason for repeat testing. Only rarely does it need to be repeated
to confirm an abnormal result.
Test results
Tests are usually completed within two weeks of the laboratory
receiving the specimen. Normal results are not currently reported
directly to each family, but your health visitor will be able
to advise you of the result. In the unlikely event that the result
of a test is abnormal, there will be no delay in arranging through
your family doctor for your baby to be seen by a paediatrician
at your local hospital.
Phenylketonuria
In this condition, a substance called phenylalanine builds up
in abnormally high amounts within the body. Very high levels can
damage the brain. Natural milk contains phenylalanine, and when
it is fed to an affected baby, phenylalanine begins to build up
immediately (although the damaging effects might not be seen for
several months). A special milk that is not harmful to the baby
can be used instead, thus reducing the risk of brain damage.
Thyroid hormone deficiency
Rarely, babies are born with a defect of the thyroid gland,
which results in the underproduction of thyroxine, the hormone
it secretes. This hormone is important for normal growth and development.
Thyroxine deficiency can be successfully treated with daily medication
to replace the missing hormone, thus promoting normal growth and
development.
Cystic fibrosis
This disorder affects the pancreas and its ability to produce
the enzymes that are essential for digestion. In untreated cases,
growth can be severely retarded. It also affects the mucous-producing
glands of the respiratory system, which can lead to chronic chest
disease. The health of those affected can be much improved if
treatment is begun as soon as possible after birth.
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