Amniocentesis is the most common diagnostic test. It involves taking some amniotic fluid, which contains cells from the baby's skin and other organs, from the uterus. These are tested and used to diagnose a range of conditions, such as Down's syndrome.
The test is usually carried out from around 15 weeks.
Why have amniocentesis?
You may want to think about having amniocentesis if you are over 37 years old, as the risk of conditions such as Down's syndrome increases with age.
It may be offered if screening tests (such as the triple test, or nuchal scan) show that your baby is high risk for Down's.
An amniocentesis test may also be recommended if you already have a child with Down's or other genetic/chromosomal abnormality, or if there is a family history of such conditions.
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Amniocentesis can also reveal other important information, which may help doctors decide about your antenatal care.
What amniocentesis can reveal
An amniocentesis test can provide the following information about your baby:
- the sex of your baby. This may be important if a baby is at risk of gender-linked disorder such as haemophilia.
- the chromosome count. Any difference fornm the normal structure could indicate your baby has a disability.
- chemical composition of the amniotic fluid. This may show up disorders caused by missing or defective enzymes.
Deciding to have amniocentesis
When deciding whether to have amniocentesis, you need to weigh up the pros of having the test, against the risks involved. The risk of miscarriage following amniocentesis is very low - less than one per cent.
You should also consider whether you would want to have your pregnancy terminated if the test results give cause for concern.
Some women decide not to have the test because the result would make no difference to them deciding whether or not to continue with their pregnancy.
One of the worst elements of having amniocentesis is the stress of waiting for the result, which can take up to three weeks to come back.
If you are considering amniocentesis you should talk to your doctor or consultant about all your concerns.
How is amniocentesis carried out?
First, you have an ultrasound scan to check the exact position of the baby and the placenta. A long hollow needle attached to a syringe is then carefully inserted into the womb, and a small amount of fluid is drawn off into the syringe for testing.
You don't need any local anaesthetic because the needle is very fine.
After the procedure, you will need to rest for the remainder of the day. You may experience slight cramping.
Information taken from Dr Miriam Stoppard's My Pregnancy Planner, DK £12.99.
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