Amniocentisis (also known as an amniotic fluid test or AFT) is a prenatal diagnostic test used to determine if a fetus has any genetic disorders or birth defects. A needle is used to extract some of the amniotic fluid that surrounds the fetus which contains chemicals that can be tested to determine genetic anomalies. An ultrasound is used to determine a safe location for the needle to enter as to not hurt the fetus. Since there is a small chance of harm that could come to the fetus or the mother amniocentisis is only used if there are risk factors for genetic disorders or birth defects present such as an abnormal ultrasound or a family history/previous birth with abnormalities. Amniocentisis can detect disorders like spina bifida or anencephaly and chromosomal abnormalities like Down syndrome.