Amniocentesis or amniotic fluid test or AFT refers to the prenatal diagnosis of chromosomal abnormalities and fetal infections. It is performed after 16 weeks of pregnancy. The fetal DNA from a small amount of cells from the amniotic fluid of the amniotic sac is sampled for genetic abnormalities by inserting a needle and extracting it. The fluid contains cells that are sloughed off by the fetus. They are separated from the amniotic fluid, grown in a culture and then microscopically examined for genetic and chromosomal abnormalities. The test is a reliable indicator of chromosomal abnormalities such as Down’s syndrome, spina bifida, muscular dystrophy, rh diseasetrisomy 13, trisomy 18, fragile X, Tay-Sachs disease, Hunter's syndrome and other metabolic disorders.