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.
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
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.
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.
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).