Are you at a higher risk of having a child with Down Syndrome? Find out where you can go for Down Syndrome testing that provide accurate results
Down Syndrome affects one in every 1000-1100 live births worldwide. While there is no medical cure or manner of prevention for Down Syndrome, early intervention can be performed starting with a Down Syndrome screening test to find out whether a mother-to-be is at risk for having a baby with this chromosomal condition.
“While the Down Syndrome test is not compulsory in Singapore, about 90% of pregnant women in Singapore take these tests,” says Dr Eunice Chua, Consultant Obstetrician and Gynaecologist at TLC Gynaecology Practice.
Tests differ according to the stage of your pregnancy. There is an initial screening during the first stage of pregnancy followed by diagnostic tests that ascertain the probability of Down Syndrome only after the results of the former are available.
Types of Down Syndrome screening in Singapore
#1: Nuchal Translucency (NT) Scan
Nuchal Translucency is an ultrasound scan which measures the width of the spinal cord at the back of the baby’s neck. It is usually performed between weeks 10 and 13 of pregnancy and is sometimes referred to as the First Trimester Screening. Doctors usually recommend this assessment as part of the Oscar Test.
- Procedure: Via an ultrasound scan
- Release period of result: As soon as the ultrasound scan is completed
- Cost: $267.50+ at NUH
Additional information on the NT Scan at National University Hospital (NUH) can be found here.
#2: Triple Test or Maternal Serum Screening
The Triple Test measures a set of three hormones (alpha-fetoprotein, HCG and Oestriol) in the blood of the pregnant mother. A risk value is calculated according to maternal age and the gestational age of the foetus at that time. Usually done around weeks 14 to 18 of pregnancy, it is also referred to as the Second Trimester Screening. Its accuracy is only 65%, thus, this test is less commonly performed during this period.
- Procedure: Sample of mother’s blood is taken
- Release period of result: About seven working days
- Cost: $149+ at Singapore General Hospital (SGH)
More information on the Triple Test or Maternal Serum Screening at the SGH is available here.
#3: OSCAR Test
Also known as “One-stop Clinic for Assessment of Risk for Foetal Anomalies,” the OSCAR test is carried out in the first trimester to screen for the risk of foetal anomalies, particularly for Down Syndrome (Trisomy 21). It involves a Nuchal Translucency (NT) Scan and a blood test.
The test is usually done between weeks 11 and 14 of pregnancy. Detection rate of Trisomy 21 by this method would be about 90%, with a false positive rate of 5%.
- Procedure: Sample of mother’s blood and ultrasound scan
- Release period of result: About two to three working days
- Cost: ~$300+ at Thomson Medical Centre
More information of the OSCAR Test at the NUH is available here.
#4: MaterniT21 Plus
MaterniT21 Plus is a new foetal DNA test launched in June 2013 that claims to have an even higher detection rate than the current first-trimester screenings.
Expectant mothers can do the new test as early as week 10 of pregnancy. These screening tests are usually done as early as possible, in case there is a need to terminate the pregnancy. However, this test does not replace the old blood test and nuchal scan.
- Procedure: Sample of mother’s blood is taken
- Release period of result: About 10 working days to two weeks as the samples are sent to a lab in the United States
- Cost: $3,000+ at Parkway Health Laboratory
More information on MaterniT21 Plus can be found here.
#5: Non-Invasive Prenatal Tests (NIPT)
Available since late 2013, doctors can detect signs of Down Syndrome by obtaining the baby’s DNA through the mother’s blood sample.
Dr Chua explains, “NIPT uses the maternal blood test to detect DNA from pregnancy. There is 99% accuracy with a low false positive of 0.1%.”
The test should only be taken if a mother is classified as high-risk in first-level screening tests, which is about five percent of all pregnant mothers.
- Procedure: Samples of mother’s blood is taken
- Release period of result: 10 to 14 working days as the samples are sent to a laboratory in the United States
- Cost: Harmony Test (~$1,200+), Panorama Screening (~$1,400+) at Thomson Medical Centre
*Check with your gynaecologist on which screening is suitable for you. Each doctor and hospital has varying facilities and your gynaecologist would be able to advise where to go for certain tests.
My test reveals a high risk of Down Syndrome, so what now?
If a screening test indicates a high risk of Down Syndrome, diagnostic tests may be performed to determine whether the baby actually has Down Syndrome. These are usually invasive options and pose a higher risk for both mother and baby.
Types of Diagnostic Tests
- Procedure: a sample of the amniotic fluid surrounding the baby is withdrawn through a needle inserted into the mother’s womb, ensuring accuracy results of close to 100%; results are released within two to three weeks
- When it is taken: after 16 weeks of gestation
- Risk of miscarriage: 0.1 to 0.3% or about one in 300 women
Chorionic Villous Sampling (CVS)
- Procedure: a sample of cells from the mother’s placenta is taken to analyse the baby’s genes, ensuring accuracy results of close to 100%; results are released within 48 hours to one week
- When it is taken: between weeks nine and 14 of pregnancy
- Risk of miscarriage: approximately one in 200
Percutaneous umbilical blood sampling (PUBS) or Cordocentesis
- Procedure: involves taking a blood sample from a vein in the umbilical cord and examining blood cells for chromosomal defects; due to its significantly higher risk of a miscarriage as compared to the previous two diagnostic tests, this is only offered as an alternative option due to unclear test results from other methods or lack of desired information obtained
- When it is taken: after 18 weeks of gestation
- Risk of miscarriage: 1.4 to 1.9%
Who are at higher risk?
The risk of Down Syndrome is directly related to the mother’s age, i.e. the older the mother, the higher the risk. For example, a 20-year-old woman has a one in 1,500 risk of having a baby with Down’s syndrome, as compared to a 35-year-old woman who has a one in 270 risk.
Additionally, about one in 100 women with a previous baby with Down Syndrome will have another. Just as Dr Chua points out, “Older mothers, history of Down Syndrome in previous pregnancy or family history of Down Syndrome [and] history of recurrent miscarriages which could be due to translocation abnormalities (i.e. scrambled chromosomes) put the risk of Down Syndrome at a higher level.”
Dr Chua also notes that there is a slightly higher risk in boys than girls, too.
While there is no treatment or prevention method available for Down Syndrome, with the available Down Syndrome screening tests in Singapore, fears may be allayed and parents are able to make appropriate choices for their family.
Palomaki, Glenn, Lee, Jo Ellen, et.al. “Technical standards and guidelines: Prenatal screening for Down syndrome that includes first-trimester biochemistry and/or ultrasound measurements.” Genetics in Medicine (2009) 11: 669–681. Web 17 August 2009.
Mums, which Down Syndrome screening Singapore test did you choose? Do share your which and your reasons for going for testing below!