Amniocentesis (amnio) is a diagnostic prenatal test used to detect chromosome disorders in a pregnancy, such as Down syndrome. It can also be used to test for other specific genetic disorders and open neural tube defects. Pregnant mothers aged 35 and over are offered amnio, due to their increased risk of having a baby with a chromosomal abnormality. An obstetrician or midwife may also suggest having the test if you have a family member with an identified genetic disease or if your screening tests or ultrasound results indicate that your pregnancy is at an increased risk for a chromosomal or other genetic disorder. Some pregnant women who don’t meet the general criteria choose to have an amnio.