Chorionic villus sampling an determine the same defect as amniocentesis, and it offers several advantages. It can be performed as early as eight weeks of gestation, which permits an earlier decision on whether or not to continue pregnancy.
Moreover, the procedure does not require penetration of the abdomen, uterus, or amniotic cavity. The procedure is lightly more risky than amniocentesis; there is a 1 to 2% chance of spontaneous abortion after the test.
A catheter is placed through the vagina and cervix of the uterus and then advanced to the chorionic villi under ultrasound guidance. About 30mg of tissue are suctioned out and prepared for chromosomal analysis.
Alternatively, the chorionic villi can be sampled by inserting a needle through the abdominal cavity, as for amniocentesis.
Chorion cells and fetal cells contain identical genetic information.
Results often are available more quickly than with amniocentesis.
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