Screening tests for Down’s syndrome and other conditions - Amniocentesis risks and benefits

Amniocentesis for genetic disorders: Amniocentesis can be offered from 15 weeks of pregnancy if:

• You have a positive or higher risk Down’s syndrome screening result

• An ultrasound scan detects an abnormality that is associated with a genetic disorder

• your past history or family history suggests that there may be a risk of your baby having a genetic or chromosomal disorder such as Down’s syndrome, sickle cell disorder or thalassaemia.

How amniocentesis is done   

Using ultrasound as a guide, a fine needle is passed through the wall of the abdomen into the amniotic fluid that surrounds your baby. Within the fluid are cells that contain the same chromosomes as your baby. A small sample of this fluid is drawn off and sent to a laboratory for testing. Most women feel only mild discomfort.

Usually, the fluid will be tested for Down’s syndrome and other serious syndromes. The results should be available within three working days.

If all the chromosomes have to be looked at, it can take up to three weeks. This test will reveal your baby’s sex, so tell your midwife or doctor whether, at this stage, you want to know if your baby is a boy or a girl.

Amniocentesis risks

This test has a 0.5–1% risk of miscarriage. At most, one test in 100 will result in pregnancy loss. When deciding whether or not to go ahead with this test, try to balance the risk of miscarriage against the value of the result to you.

Help and support

Antenatal Results and Choices (ARC) helps parents with all issues associated with antenatal testing and its implications. They can give you more advices or put you in touch with parents who decided to continue with a pregnancy in which an abnormality had been detected.