Definition: what is amniocentesis? Amniocentesis is an amniotic liquid examination that allows the detection of genetic anomalies and chromosome problems. It is especially used when screening for Down’s syndrome. Amniocentesis is an examination regularly prescribed to pregnant women but it does have some risks. How is the amniocentesis examination carried out? Amniocentesis is generally done around the fourth month of pregnancy. The exam is done in a hospital or a maternity ward and always under ultrasound surveillance. A needle guided by the ultrasound is inserted into the mother’s abdomen in order to extract between 15 and 20 cubic centimetres of amniotic liquid. This only lasts a few minutes. The results of amniocentesis aren’t available for 3 to 4 weeks after the exam. In case of a significant anomaly, a therapeutic abortion will be suggested. Why do an amniocentesis exam? Amniocentesis is generally recommended to pregnant women over the age of 38 because from this age, the risk of Down’s syndrome is greatly increased (1 in 100 pregnancies). In addition, amniocentesis is advised in case of a family history that suggests suspected infections, nuchal translucency during an ultrasound (neck thickness wider than average), deformations or growth retardation. Risks of amniocentesis Amniocentesis isn’t an examination with no risks. In some cases, it can cause a miscarriage in the two weeks following the examination. The risks are however very small and only occurs in between 0.5 to 1% of cases.