What is Chorionic Villus Sampling (CVS)?
Chorionic Villus Sampling (CVS) is a prenatal diagnostic procedure used to detect genetic abnormalities in a developing fetus. It involves taking a small sample of tissue from the placenta, called the chorionic villi, which shares the baby's genetic makeup. This test is typically performed between the 10th and 13th weeks of pregnancy.
Why is CVS Performed?
CVS is primarily performed to identify chromosomal abnormalities such as Down syndrome, as well as other genetic disorders like cystic fibrosis, Tay-Sachs disease, and sickle cell anemia. It is often recommended for women who have a family history of genetic disorders, are of advanced maternal age, or have had abnormal results from other prenatal screenings.
1. Transcervical CVS: A catheter is inserted through the cervix to reach the placenta and collect the sample.
2. Transabdominal CVS: A needle is inserted through the abdomen and uterus to reach the placenta and obtain the sample.
Both methods are guided by ultrasound to ensure accuracy and minimize risks.
- Miscarriage: The risk of miscarriage is approximately 1 in 100 to 1 in 200.
- Infection: There's a small risk of infection at the site where the sample is taken.
- Rh Sensitization: If the mother is Rh-negative, she may require an injection of Rh immunoglobulin to prevent complications.
- Bleeding or Cramping: Some women may experience light bleeding or cramping after the procedure.
- A family history of genetic disorders.
- Abnormal results from other prenatal tests, such as the first trimester screening or non-invasive prenatal testing (NIPT).
- A previous child with a genetic disorder.
- Maternal age of 35 years or older at the time of delivery.
- Discussing the procedure, risks, and benefits with a healthcare provider.
- Undergoing a detailed ultrasound to locate the placenta.
- Emptying the bladder before the procedure if advised.
- Arranging for someone to drive you home after the procedure, as rest is recommended.
- Monitoring for any signs of infection, such as fever or unusual discharge.
- Avoiding strenuous activities for a few days.
- Reporting any heavy bleeding or severe cramps to a healthcare provider immediately.
How Accurate is CVS?
CVS is highly accurate, with a diagnostic accuracy rate of around 98-99% for chromosomal abnormalities. However, it does not detect neural tube defects, which may require additional testing such as a second-trimester ultrasound or amniocentesis.
- Amniocentesis: Usually performed between the 15th and 20th weeks of pregnancy, this procedure involves taking a sample of the amniotic fluid surrounding the fetus.
- Non-Invasive Prenatal Testing (NIPT): A blood test that can screen for certain genetic conditions as early as 10 weeks into the pregnancy.
- First Trimester Screening: A combination of ultrasound and blood tests to assess the risk of chromosomal abnormalities.
Conclusion
Chorionic Villus Sampling (CVS) is a valuable prenatal diagnostic tool for detecting genetic abnormalities early in pregnancy. While it carries some risks, the benefits of early diagnosis can be significant for families with a history of genetic disorders or other risk factors. It is crucial to discuss with your healthcare provider to determine if CVS is the right choice for you.
