When is chorionic villus sampling recommended for Down syndrome?

Chorionic villus sampling, often called CVS, takes a small sample of placental tissue. The cells can be examined for chromosome differences, including the extra chromosome associated with Down syndrome. CVS is a diagnostic test, while ultrasound and blood screening estimate chance rather than confirming a chromosome condition.

CVS is usually discussed early in pregnancy, within a specific clinical window. It is not offered to everyone automatically. A specialist considers the screening result, ultrasound findings, family history, previous pregnancy history, and your preferences.

Ask for a clear explanation of what the result can and cannot identify, how the sample will be collected, and when results may be available. Discuss alternatives, including continuing screening without an invasive test or considering another diagnostic test later in pregnancy.

Tell the maternity team about your blood group, medicines, bleeding problems, allergies, and any current pregnancy symptoms. Make sure you have time to consider the information and support that would help you decide.

After CVS, contact your maternity team for vaginal bleeding, fluid leakage, increasing cramps, fever, or feeling unwell. Seek urgent help for heavy bleeding, severe abdominal pain, dizziness, or collapse.

Ask what raised the chance of Down syndrome, whether CVS is suitable at this stage, what the possible results mean, and what support is available while waiting.