amniocentesis

a procedure carried out to sample the AMNIOTIC FLUID surrounding a FOETUS . A fine needle is inserted through the abdominal wall of the mother and the amniotic sac is pierced so that a small quantity of fluid can be drawn off. The amniotic fluid contains ALPHA FETOPROTEIN and cells from the embryo, and various disorders such as DOWN'S SYNDROME and SPINA BIFIDA can be detected. It is usually carried out between the 16th abd 20th week of pregnancy if a foetal abnormality is suspected.