CVS or amnio test: what should you know?

Chorionic villus sampling collects a small sample from the placenta. Amniocentesis collects a small sample of amniotic fluid, which contains cells from the pregnancy. Both can examine chromosomes, but they are not interchangeable in every situation. The choice depends on gestational stage, the question being investigated, ultrasound findings, family history and the options available through your maternity team. A non-invasive prenatal test screens for selected chromosome differences but does not replace a diagnostic test when confirmation is needed.

Ask what each test can detect, how the sample is collected, when results are expected and what an uncertain or unexpected result could mean. Discuss the procedure with a fetal medicine or genetics team, including the small risk of pregnancy complications and whether your blood group requires additional care. Take time to consider how results would affect pregnancy planning. Bring your ultrasound reports and a list of medicines, and arrange support for the appointment if that would help.

Follow the team’s instructions and contact them urgently for heavy bleeding, fluid leakage, persistent severe abdominal pain, fever or contractions. Mild cramping or brief spotting can occur, but your own maternity service should explain what to monitor and how to reach them. Do not wait for planned results if you feel acutely unwell.

Ask which test answers your specific question, why it is being offered now, whether screening has already changed the next step, and what support is available while you await results.