Dr. Rajeeb Jena

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Invasive Procedures and Interventions

Chorionic Villus Sampling (CVS)

What is Chorionic Villus Sampling?

Chorionic Villus Sampling (CVS) is an invasive prenatal diagnostic test performed between 10 and 13 weeks of pregnancy. It involves collecting a small sample of placental tissue (chorionic villi) to analyze fetal chromosomes and detect genetic disorders.

Why is it done?

  • To diagnose chromosomal abnormalities such as Down syndrome, Trisomy 18, and other genetic conditions.
  • Recommended if there is a family history of genetic disorders.
  • Advised when first trimester screening tests (e.g., NIPT or combined screen) indicate high risk.
  • For women aged 35 years or older at delivery due to increased aneuploidy risk.

When is CVS performed?

CVS is ideally carried out between 10 weeks and 13 weeks + 6 days of gestation. Earlier sampling may yield insufficient tissue; later sampling overlaps with amniocentesis timing.

How is the procedure done?

  • **Transabdominal approach:** Under ultrasound guidance, a thin needle is inserted through the abdomen into the placenta to collect villi.
  • **Transcervical approach:** A catheter is passed through the cervix under ultrasound guidance to obtain placental tissue.
  • The sample is sent to a genetic laboratory for chromosomal and molecular analysis.
  • The entire procedure takes about 10–20 minutes and is performed under local anesthesia.

Benefits and Limitations

Benefits:

  • Early definitive diagnosis of genetic disorders.
  • Results available faster (within 7–10 days) compared to amniocentesis.

Limitations:

  • Invasive procedure with a small risk of miscarriage (~0.5–1%).
  • Cannot detect neural tube defects (requires later ultrasound or amniotic fluid AFP).
  • Risk of infection, bleeding, or Rh sensitization (anti-D prophylaxis may be needed).

Frequently Asked Questions (FAQs)

What preparation is needed?

No special preparation; a full bladder is usually not required.

CVS is generally safe but carries a small miscarriage risk of around 0.5–1%.

Local anesthesia is used; you may feel mild cramping or pressure.

Results are typically available in 7–10 days.

Genetic counseling is offered to discuss options and management.