Down syndrome is a genetic condition that results from an extra copy of chromosome 21. This extra genetic material can cause developmental delays, intellectual disability, and certain physical characteristics. While there is no cure for Down syndrome, early intervention and support can help individuals with Down syndrome lead happy and fulfilling lives.

Prenatal screening for Down syndrome has become increasingly common and can help expectant parents make informed decisions about their pregnancy, prepare for the future, and plan for any necessary medical interventions or support. In this article, we will explore the different types of Down syndrome screening, how they work, and what to expect during the screening process.

Types of Down Syndrome Screening

Non-invasive prenatal testing (NIPT): NIPT is a blood test that analyses the foetal DNA present in the mother's blood to detect chromosomal abnormalities, including Down syndrome. This test is typically performed between 10-14 weeks of pregnancy and is considered highly accurate, with a detection rate of over 99%.
Combined first-trimester screening: Combined first-trimester screening involves two parts: a blood test and an ultrasound. The blood test measures the levels of two hormones, pregnancy-associated plasma protein-A (PAPP-A) and human chorionic gonadotropin (hCG), in the mother's blood. The ultrasound measures the thickness of the skin at the back of the foetal neck, known as the nuchal translucency (NT). This test is typically performed between 11 to 14 weeks of pregnancy and has a detection rate of around 85%.
Quadruple screen: The quadruple screen is a blood test that measures the levels of four substances in the mother's blood: alpha-fetoprotein (AFP), hCG, unconjugated estriol (uE3), and inhibin-A. This test is typically performed between 15 and 20 weeks of pregnancy and has a detection rate of around 80%.
Amniocentesis: Amniocentesis involves inserting a needle through the mother's abdomen into the amniotic sac to obtain a sample of amniotic fluid. This sample can be analysed for chromosomal abnormalities, including Down syndrome. Amniocentesis is typically performed between 15-20 weeks of pregnancy and is considered highly accurate, with a detection rate of over 99%.

How Does Down Syndrome Screening Work?

Non-invasive prenatal testing (NIPT) and the quadruple screen are both blood tests that measure the levels of certain substances in the mother's blood. NIPT specifically looks for fragments of foetal DNA in the mother's blood, while the quadruple screen looks for levels of AFP, hCG, uE3, and inhibin-A.

The combined first-trimester screening involves both a blood test and an ultrasound. The blood test measures the levels of PAPP-A and hCG in the mother's blood, while the ultrasound measures the thickness of the skin at the back of the foetal neck, known as the nuchal translucency (NT). The results of both the blood test and the ultrasound are used together to estimate the risk of Down syndrome.

Amniocentesis involves inserting a needle through the mother's abdomen into the amniotic sac to obtain a sample of amniotic fluid. This sample can be analysed for chromosomal abnormalities, including Down syndrome.

What to Expect During the Screening Process:

Non-invasive prenatal testing (NIPT) and the quadruple screen are both simple blood tests that can be done in a doctor's office or lab. The blood sample is typically taken from the mother's arm and sent to a lab for analysis. Results are usually available within a week.

In conclusion, screening for Down's syndrome is an important part of prenatal care for many expectant parents. Through various screening tests, such as ultrasound, blood tests, and non-invasive prenatal testing (NIPT), healthcare providers can determine the likelihood of a foetus having Down's syndrome. While these screening tests are not 100% accurate, they can help parents make informed decisions about their pregnancy and plan for any necessary medical or emotional support for their child.

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1. How accurate are the different types of Down syndrome screening?

NIPT is considered highly accurate, with a detection rate of over 99%. Combined first-trimester screening has a detection rate of around 85%, while the quadruple screen has a detection rate of around 80%. Amniocentesis is also considered highly accurate, with a detection rate of over 99%.

2. When is Down syndrome screening typically performed?

The timing of Down syndrome screening depends on the type of screening. NIPT is typically performed between 10 and 14 weeks of pregnancy, while combined first-trimester screening is typically performed between 11 and 14 weeks. The quadruple screen is typically performed between 15-20 weeks, and amniocentesis is also typically performed between 15-20 weeks.

3. Are Down syndrome screenings mandatory?

Down syndrome screenings are not mandatory, but they are recommended by many healthcare providers for expectant parents to know more about their unborn baby and potential genetic conditions.

4. What are the risks of Down syndrome screening?

The risks of Down syndrome screening are generally low, but some procedures, such as amniocentesis, do carry a small risk of miscarriage or other complications.

5. What happens if Down syndrome is detected during screening?

If Down syndrome is detected during screening, expectant parents can work with their healthcare provider to develop a plan for medical care and support for their child, including early intervention services and medical treatments. They may also consider genetic counselling to understand the condition and potential risks for future pregnancies.

6. What if I choose not to undergo Down syndrome screening?

Choosing not to undergo Down syndrome screening is a personal decision, and expectant parents should discuss their options and concerns with their healthcare provider. It is important to remember that not all cases of Down syndrome are detectable by screening and that there are still resources and support available for families who have a child with Down syndrome.