The Portland Hospital
205-209 Great Portland Street W1W 5AH London
Amniocentesis
A test which involves extracting a small sample of the amniotic fluid surrounding your unborn baby to test for a genetic condition.
What is an amniocentesis test?
You'll be offered amniocentesis if you have a higher than average chance of giving birth to a child with a genetic abnormality.
This could be because:
- your antenatal screening test has indicated there may be a problem, such as Down's syndrome, Edwards' syndrome or Patau's syndrome
- you've had these problems before
- you have a family history of a genetic condition, such as sickle cell disease, thalassaemia, cystic fibrosis or muscular dystrophy, and an abnormality is detected in your baby during a routine ultrasound scan
This test can also be used to determine the sex of your child.
It's important to remember you don't have to have the test. It's entirely your decision.
Need to know
During the procedure a thin needle is inserted through the wall of your belly in an area numbed by local anaesthetic. It's guided using an ultrasound image. The needle is used to take a sample of fluid from the amniotic sac surrounding your baby. It takes about 10 minutes and is usually performed between the 15th and 20th weeks of pregnancy. It could be performed later than this, but there is some risk connected to performing it any earlier. The experience 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.
There is no special preparation required beforehand, and you can eat and drink as normal. You may be asked to avoid going to the toilet for a few hours before the test as the procedure is sometimes made easier when your bladder is full. Your consultant will advise you about this before your appointment.
After the procedure it's normal to have cramps similar to period pain and light vaginal bleeding called "spotting" for a day or two. You also may wish to avoid any strenuous activity for at least 24 hours after the procedure.
Contact your consultant should you experience any of the following:
- persistent or severe pain
- a high temperature of 38C or more
- chills or shivering
- discharge or clear fluid from the vagina
- contractions (when your abdomen tightens then relaxes)
Your consultant will be able to tell you when to expect the results of the test.