Down Syndrome FAQ
with our Genetic Counselor

What is Down Syndrome?

  • Down syndrome individuals have spesific facial feature and have severe mental retardation. Many will also have heart and bowel conditions that require surgery. They are unable to attend normal school.
  • It is the most common genetic (chromosomal) Condition discovered in babies where there is an extra chromosome 21 (trisomy 21).

How does Down Syndrome occur?

  • Babies with Down syndrome have an extra chromosome-21.
  • The affected ovum where failure of division of chromosome 21 occurred will have this extra chromosome 21.
  • When it is united with a sperm the conception will have an extra chromosome 21, causing Down syndrome in the affected baby.
  • The possibility of failure for chromosomes to divide in mothers’ ovum (egg) is a spontaneous phenomenon that increases with age of the mother.
  • The average rate is 1 per 1000 pregnancies
    The probability is closely related to the mother’s age with the chance increasing the older the mother. Every pregnancy has a chance. A 30 year old has a 1 in 550 chance. A 35 year old has a 1 in 270 chance.

There are no cases of Down Syndrome in my family. Can my baby get it?


  • Most Down Syndrome is spontaneous and can happen in any pregnancy.
  • See Question 2 above

What happens when a baby has Down Syndrome (clinical features)?

  • Babies with Down syndrome have a characteristic appearance.
  • 98% have major mental deficiencies and can only attend schools for special kids.
  • Many have structural problems such as hole in the heart or blocked intestines that may require surgery after birth.
  • They are almost always dependent on their parents or social welfare organizations for life. Very few are independent.
  • There is no treatment available.

Why are there specialized tests to detect Down Syndrome in pregnancy?

  • Down syndrome can appear normal on normal on detailed scans 30% of the time.
  • Specialized screening tests increase their detection rate.

What screening tests are available for the detection of Down Syndrome in pregnancy?

  • The 1st Trimester Detailed Genetic Scan done between 11 and 14th week of pregnancy (FTScan) has a 70% detection
  • FT-Scan + risk calculation (accredited centres) has close to 90% detection (depends on protocol used by the sonographer – Aseana has a 90% detection rate on ultrasound alone)
  • Combined blood+FTScan, cFTS, has a detection of 95%
  • Fetal DNA tests (maternal blood), known as NIPT, has a detection of 99.99%
    These tests carry no risks to baby.

Can the 2nd trimester Detailed Structural Scan detect babies with Down Syndrome?

  • Yes.
  • 30-40% of Down Syndrome are detected at the “Detailed Scan” at 20 weeks (2nd trimester)
  • The detection rate of Down Syndrome is not as high as other specific screening tests described in Q5.

Why is the Triple Test or the Double Test not listed?

  • These tests have a lower detection rate than ultrasound alone in the 1st trimester Detailed Genetic Scan (FTScan).
  • These tests are rarely offered these days unless earlier options are missed.

Is there a diagnostic test (confirmatory)?

  • Yes. Fetal or placental cells are sampled by amniocentesis or placenta biopsy (chorionic villous sampling, CVS) and sent for confirmatory genetic testing.
  • The invasive procedures however carry a miscarriage risk of 0.5 to 1%

What is the best approach? Which test should I do?

  • Start with the 1st Trimester Detailed Genetic Scan, FTScan, for a baseline genetic assessment as there are many other conditions too. If an abnormality on ultrasound is picked up other tests may be more relevant.
  • If the FTScan is normal, consider further Down Syndrome testing as your budget would allow.

What are the possible results after I opt for a specific screening test?

  • Tests typically report back as Low Risk or High Risk.
  • A Low Risk result means the possibility of Down Syndrome is reduced significantly. But it could be falsely negative, ie baby has Down Syndrome but result flagged as Low Risk – this is uncommon.
  • A High Risk result means that the possibility of Down Syndrome is significantly increased. But there is still a possibility of a false positive, ie baby is actually normal but results flagged as High Risk – this is uncommon.

Does a High Risk result mean my baby has Down Syndrome?

  • No. See Question 8
  • There is still a possibility of baby being normal. Each test has its own false positive rate where normal babies are also flagged as High Risk.
  • A diagnostic confirmatory test should be done after a High Risk result.