Amniocentesis & CVS

What is Amniocentesis & CVS?

Amniocentesis and chorionic villus sampling (CVS) are invasive diagnostic procedures used to obtain fetal cells for chromosomal and genetic analysis. CVS is performed between 11 and 14 weeks by sampling placental tissue. Amniocentesis is typically performed after 15 weeks by sampling amniotic fluid. Both provide definitive genetic information about the baby, unlike screening tests which only estimate risk.

Why is it a Concern?

These procedures carry a small risk of miscarriage (approximately 0.1–0.5%). They are offered when the clinical benefit of a definitive diagnosis outweighs this small procedural risk — typically when screening has identified an elevated risk or when a specific genetic condition needs to be tested for.

Signs & Symptoms

• High-risk screening result (NIPT, combined screening, or ultrasound findings)
• Previous pregnancy affected by a chromosomal or genetic condition
• Known parental carrier status for a genetic condition
• Ultrasound findings suggesting a chromosomal abnormality
• Parental request for definitive prenatal diagnosis

How It is Monitored

Both procedures are performed under continuous ultrasound guidance. After the procedure, a short period of rest is recommended. Results for rapid testing (FISH or QF-PCR) are usually available within 2–3 days, with full karyotype results in 2–3 weeks. Microarray or specific gene testing may take longer.

Why See an MFM Specialist?

MFM specialists are trained and experienced in performing these delicate procedures, minimising risk through precise ultrasound guidance. They also provide pre-procedure counselling to help families understand the risks, benefits, and implications of the results.