Intro
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Amniocentesis is a test you may be offered
during pregnancy to check if your baby has a genetic or chromosomal condition,
such as Down's, Edwards' or Patau's syndromes.
Amniocentesis (also referred to as amniotic
fluid test or AFT) is a medical procedure used in prenatal diagnosis of
chromosomal abnormalities and fetal infections, and also for sex determination,
in which a small amount of amniotic fluid, which contains fetal tissues, is
sampled from the amniotic sac surrounding a developing fetus, and then the
fetal DNA is examined for genetic abnormalities.
Why
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Amniocentesis isn't routinely offered to
all pregnant women. It's only offered if there's a higher chance your baby
could have a genetic condition.
This could be because:
an antenatal screening test has suggested
there may be a problem, such as Down's syndrome, Edwards' syndrome or Patau's
syndrome.
you've had a previous pregnancy with these
problems
you have a family history of a genetic
condition, such as sickle cell disease, thalassaemia, cystic fibrosis
ormuscular dystrophy, and an abnormality is detected in your baby during a
routine ultrasound scan
How
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Amniocentesis is usually carried out
between the 15th and 20th weeks of pregnancy, but may be performed later than
this if necessary.
Although it can be performed earlier, this
may increase the risk of complications of amniocentesis and is usually avoided.
During the test, a long, thin needle is
inserted through your abdominal wall, guided by an ultrasound image. The needle
is passed into the amniotic sac that surrounds the foetus and a small sample of
amniotic fluid is removed for analysis.
The test itself usually takes about 10
minutes, although the whole consultation may take about 30 minutes.
Amniocentesis is usually described as being
uncomfortable rather than painful. Some women describe experiencing a pain
similar to period pain or feeling pressure when the needle is taken out.
Risks
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Before you decide to have amniocentesis,
the risks and possible complications will be discussed with you.
One of the main risks associated with
amniocentesis is miscarriage, which is the loss of the pregnancy in the first
23 weeks. This is estimated to occur in 0.5% to 1% of women who have
amniocentesis.
There are also some other risks, such as
infection or needing to have the procedure again because it wasn't possible to
accurately test the first sample that was removed.
The risk of amniocentesis causing
complications is higher if it's carried out before the 15th week of pregnancy,
which is why the test is only carried out after this point.
Results
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The first results of the test should be
available within three working days and this will tell you whether Down's,
Edwards' or Patau's syndrome has been discovered.
If rarer conditions are also being tested
for, it can take two to three weeks or more for the results to come back.
If your test shows that your baby has a
genetic or chromosomal condition, the implications will be fully discussed with
you. There's no cure for most of the conditions amniocentesis finds, so you'll
need to consider your options carefully.
You may choose to continue with your
pregnancy, while gathering information about the condition so you're fully
prepared, or you may consider having a termination (abortion).
