Amniocentesis is an exam that is done in pregnancy to discover certain abnormalities in the baby, such as Down syndrome, but it is not a routine exam, because it carries some risks. Because of its purpose, it is categorized as a diagnostic test, to confirm suspicions. Also called a "villus biopsy," the test consists of taking a sample of the amniotic fluid from the uterus and examining it. It is only indicated in cases of changes in routine exams, such as morphological ultrasound, of the first trimester, or non-invasive prenatal diagnosis.
Cronic Villus sampling utilizes either a catheter or needle to biopsy placental cells that are derived from the same fertilized egg as the fetus. During amniocentesis, a small sample of the fluid that surrounds the fetus is removed.
