Chorionic Villus Sampling (CVS)
Definition
A procedure in which a sample is taken from placental tissue. Because the tissue obtained carries the same genetic makeup as the fetus, genetic testing can be performed on it.
When it is done: Between the 10th and 13th weeks of pregnancy, earlier than amniocentesis.
Purpose
Prenatal diagnosis of chromosomal disorders and genetic diseases. It provides the same genetic information as amniocentesis, but at an earlier stage.
Results
Like amniocentesis, it is a diagnostic test; it gives a definitive result, not a probability.
Risks and Limitations
It carries a risk of miscarriage, and this risk is slightly higher than with amniocentesis.
Comparison with amniocentesis:
| CVS | Amniocentesis | |
|---|---|---|
| Timing | Weeks 10 to 13 | Weeks 15 to 20 |
| Advantage | Earlier result | Lower miscarriage risk |
| Disadvantage | Slightly higher miscarriage risk | Later result |
| Neural tube defect | Cannot detect (AFP cannot be measured) | Can detect |