Amniocentesis

Amniocentesis

Amniocentesis is a test that is offered to pregnant women. The most common reason for having the test is to check whether a baby has any disorders or abnormalities, such as Down syndrome. It is offered to pregnant women who have a higher chance of carrying a child with certain conditions.

Determining the need for an amniocentesis

A midwife or doctor will suggest having an amniocentesis test if:

• The mother has a family history of a genetic condition
• An abnormality has been detected during an ultrasound
• The mother has had other problem pregnancies
• An antenatal screening test shows there is a problem
• The mother is of a certain age

It is up to the mother of the unborn child to decide whether or not they want to have the test.

How is an amniocentesis performed?

The test is carried out between the 15th and 20th weeks of pregnancy. There are times when it may be performed at a later week. Amniocentesis involves inserting a long needle through the abdominal wall. This is guided by an ultrasound image. The thin needle is then pushed into the amniotic sac that surrounds the foetus. A sample of amniotic fluid is then removed for testing. It is not a painful procedure. The results can take a few days or a couple of weeks to be returned.

What problems can the test detect?

An amniocentesis test is used to detect:

• Chromosomal disorders including Down syndrome, trisomy 13, trisomy 18 and sex chromosome abnormalities
• Genetic disorders including Tay-Sachs disease, cystic fibrosis and sickle cell
• Neural tube defects including anencephaly and spina bifida

The test cannot detect birth defects, such as cleft lip and heart problems. However, these problems can be picked up on an ultrasound.