Amniocentesis is a prenatal test that allows one’s healthcare practitioner to diagnose health concerns, genetic diseases, and chromosomal abnormalities in the womb by extracting a sample of amniotic fluid. This is the fluid that surrounds the baby in the uterus during development, where fetal cells that contain important health information are present. Amniocentesis is typically performed when an expectant mother is between 15 and 18 weeks pregnant and, due to the small level of risk, is often times only advised for women who have an increased risk of giving birth to a baby with genetic defects. Amniocentesis cannot detect structural birth defects. It is also the most accurate way to determine the sex of the baby before birth.