This test is usually carried out between 15 - 20 weeks of pregnancy, although this may vary. A needle is inserted through the abdomen and removes a small amount of the amniotic fluid surrounding the baby. As with CVS, ultrasound is used to find the best location to take the fluid from and to guide the needle.
The amniotic fluid contains some of the baby's cells that have shed naturally. These cells can then be analysed in the laboratory.
The risk of miscarriage associated with amniocentesis is about 1%.
