FAQ on Down Syndrome
This article is a compilation of most frequently asked questions for pregnant women compiled by our author who are experts in O&G. Over 2000 answers & tips are provided to help educate and engage the women in Singapore.
What is Down Syndrome?
- Down syndrome is a genetic disorder caused when abnormal cell division results in an extra full or partial copy of chromosome 21.
- This extra genetic material causes the developmental changes and physical features of Down syndrome. Down syndrome varies in severity among individuals, causing lifelong intellectual disability and developmental delays.
- It’s the most common genetic chromosomal disorder and cause of learning disabilities in children.
- It also commonly causes other medical abnormalities, including heart and gastrointestinal disorders. (Definition adapted from Mayo Clinic)
What Test are available for Downs Syndrome?
- A number of tests are available to screen for Down syndrome, and they usually can be done from 11 weeks onwards.
- 11 to 13 Weeks
- Between 11-13, the most common and widely used form of screening is called the First Trimester Screening (FTS), also called the Oscar test. This test consists of a simple blood test and an ultrasound to look the neck thickness and nose bone of the baby. These parameters are combined to give you an overall risk. A calculated risk smaller than 1/300 of having Down syndrome is considered low-risk. A calculated risk greater than 1/100 is considered high-risk. A calculated risk between 1:100 and 1:300 is considered medium risk. A medium risk or high-risk test result warrants further investigation.
- More then 13 Weeks
- If you have missed the 11-13 week screening period, fret not, there are still two alternative screening option! One is called Maternal Serum Screening (MSS). It is a simple blood test that uses several hormonal levels to calculate an overall risk, and can be done in most maternity hospital. However, this test is not as accurate as the Oscar test/First Trimester Screening done between 1-13 weeks. Another more accurate test is called the Non-Invasive Prenatal Test (NIPT).
- About NIPT test
- NIPT (Non-Invasive Prenatal Test) is a recent innovative medical development, where a special blood test is done to extract fetal DNA from the maternal bloodstream. It is a non-invasive test that enjoys high sensitivity of 99% (i.e. very likely to pick up almost all Down Syndrome cases), compared to 90% sensitivity in the First Trimester Test. Keep in mind that it is a screening test, not a diagnostic test. Some mothers feel adequately confident by the result a 99% sensitive screening test, while others prefer to go for a definite diagnostic test – namely amniocentesis or chorionic vili sampling (CVS). Click the link to find out more.
- Downs Syndrome Diagnostic Test
- If you receive a high-risk Down Syndrome screening test, we would recommend that you go for a diagnostic test. Since you are currently before 13 weeks gestation, the most appropriate diagnostic test is chorionic vilic sampling (4.1). Cells from tiny fingerlike projections on your placenta called the chorionic villi are taken and sends them to a lab for genetic analysis. This procedure is only done by obstetric specialists.
- If you receive a high-risk Down Syndrome screening test, we would recommend that you go for a diagnostic test. Since you are currently at or after your 13 weeks of gestation, the most appropriate diagnostic test is amniocentesis (4.1). A small amount of amniotic fluid, which contains fetal tissues, is sampled from the amniotic sac surrounding a developing fetus, and then the fetal DNA is examined for genetic abnormalities. This procedure is only done by obstetric specialists.