Down Syndrome Tests Test
Down syndrome tests check whether a developing fetus may have Down syndrome, a chromosome disorder caused by an extra copy or piece of chromosome 21.
What this test measures
Down syndrome tests measure the chance or presence of an extra copy or piece of chromosome 21 in a fetus's cells or DNA. Screening tests estimate risk using blood samples and ultrasounds, while diagnostic tests confirm the condition by examining fetal cells or DNA.
What your results mean
Reference ranges vary by laboratory and by your age and sex. MedlinePlus does not publish a single normal range for this test — always read your result against the range printed on your own lab report and discuss it with your provider.
Higher-than-normal results
A positive screening test result means that your baby's chance of having Down syndrome is higher than average. But a high risk doesn't mean your baby will have Down syndrome.
Lower-than-normal results
A negative/normal screening test result means that your baby is unlikely to have Down syndrome. But a screening test can't guarantee that your baby won't have Down syndrome.
Frequently asked questions
What is Down syndrome?
Down syndrome is a chromosome disorder caused by having an extra copy or piece of chromosome 21.
What are the two basic types of Down syndrome tests?
Screening tests estimate the chance of Down syndrome, and diagnostic tests confirm whether it is present.
What does a positive screening test result mean?
It means your baby's chance of having Down syndrome is higher than average, but it does not mean your baby will have Down syndrome.
What does a negative screening test result mean?
It means your baby is unlikely to have Down syndrome, but it cannot guarantee that your baby won't have Down syndrome.
Can diagnostic tests predict how much Down syndrome will affect my baby?
No, diagnostic tests can tell you whether your baby has Down syndrome, but they cannot predict how much it will affect your baby's health and abilities.
Related lab tests
Sources
- MedlinePlus: Down Syndrome Tests — NIH MedlinePlus
Last updated . Information is aggregated from official public sources and is not a substitute for professional medical care.