What is Amniocentesis?

Amniocentesis is a diagnostic test that is carried out during pregnancy to assess whether the unborn baby (foetus) could develop, or has developed, an abnormality or serious health condition. The test can detect a number of conditions including Down’s syndrome, spina bifida and sickle cell anemia.

It is one of two diagnostic tests which are offered to women with a high screening result, the other being chorionic villus sampling (CVS). CVS can be performed from weeks 10-22 of your pregnancy although it usually takes place between weeks 11-13. Amniocentesis is usually carried out between weeks 15-18 of pregnancy.

Amniocentesis involves using a fine needle to take a small sample of the amniotic fluid which surrounds your baby. It is a widely used procedure and takes about ten minutes. You will have an ultrasound scan first to check the position of your baby and the scan will continue throughout the procedure. A fine needle is then inserted through your abdomen, into your womb, to take the sample of amniotic fluid. The fluid contains cells from your baby which will be examined in the laboratory while their chromosomes are counted. It can take up to 18 days to get these results back.

Unfortunately there is a small risk of miscarriage with both the diagnostic tests. With CVS the risk is about 1-2% and with amniocentesis the risk is about 1% but these figures do vary between hospitals, so it is always worth asking what the miscarriage rates in your particular hospital are. Your midwife should be able to give you this information.

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