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Here’s How Doctors Find Out Whether a Baby Will Be Born With Down Syndrome

Extra copies of chromosome 21 lead to a genetic disorder known as Down syndrome where certain symptoms result, such as cognitive dysfunction and other developmental delays. Distinctive physical features include upward-slanting eyes, a flattened bridge of the nose, only one crease on the palm (instead of the customary three), and low muscle tone, but not everyone with Down syndrome has all of these features.

Here's how doctors find out whether a baby will be born with Down syndrome (Shutterstock)
Here’s how doctors find out whether a baby will be born with Down syndrome (Shutterstock)

In an interview with HT Lifestyle, Dr Sonal Kumta, Senior Consultant-Obstetrician and Gynecologist at Fortis Hospital, Mulund explained, “Down syndrome is a condition or genetic abnormality where trisomy 21 (there are three instead of 2 chromosomes) occurs . It affects a person’s intellectual development and can cause congenital abnormalities such as heart defects and poor quality of life.

He elaborates, “A pregnant woman can undergo the test to check if there is any genetic abnormality in the foetus. They can opt for screening in the first trimester (13 weeks) and undergo nuchal translucency (NT), which is an ultrasound-based test and a dual marker test (blood test) that includes pregnancy-associated plasma protein-A (PAPP-A). a) and the pregnancy hormone known as human chorionic gonadotropin (hCG). Both these tests have good reliability, so pregnant women should undergo these tests to detect common genetic problems. After the results are out, it is important to visit your gynecologist for further evaluation.”

Dr. Shiva Murarka, Senior Scientist-Reproductive Genomics, Newberg Center for Genomic Medicine, said, “Routine prenatal testing is offered to expectant mothers for a variety of reasons and at different stages of pregnancy. They include screening exams including blood tests (including biochemical marker screening) and ultrasound exams that can predict the likelihood that your baby will be born with a number of diseases, such as Down syndrome.

Talking about prenatal testing options, she said, “Screening tests increase the chances of having a baby with Down syndrome. Although the test does not pose any risk of miscarriage, the test can reveal whether the fetus is affected. In contrast, diagnostic tests have a low miscarriage risk (often less than 1%), but they are accurate in detecting various fetal abnormalities. The American College of Obstetricians and Gynecologists (ACMG) recommends offering screening tests and diagnostic test options for Down syndrome to all pregnant women, regardless of age.

Dr. Shiv Murarka suggests:

A screening test

It is non-invasive in nature and the test is done with the mothers blood

Non-invasive prenatal test (NIPS)

Performed as early as 9 weeks of pregnancy and results are available within 7 days.

B. Diagnostic Tests

It is invasive in nature and is being performed on amniotic fluid (AF) or chorionic villus sample (CVS).

An amniocentesis procedure for genetic testing is usually done at 16-20 weeks while CVS is done at 11-13 weeks of pregnancy.

1. Traditionally chromosomal karyotyping and fluorescent in situ hybridization (FISH).

Karyotyping usually takes 15-20 days to report as it involves the process of cell culture.

FISH is the gold standard for the detection of five common aneuploidies. It is the only technique capable of detecting low-level mosaicism.

2. Microarray

It is a very high resolution molecular cytogenetic technique. Recently, Neuberg launched the Cyto-One test, an advanced version of existing microarray tests. Microarray can detect microdeletions/microduplications providing better coverage of embryonic disorders.

3. PAN – Prenatal Aneuploidy Test

The PAN test is capable of detecting abnormalities on all chromosomal and sub-chromosomal regions, with the advantage that it has better sensitivity and detection capability than the current test. It can detect more disorders and covers all chromosomes instead of just 5, which increases its scope and coverage. The test has a quick turnaround time of 48-72 hours and costs about the same as previous tests, making it more accessible to doctors and patients.

Dr. Shiva Murarka concluded, “We recommend that you talk to your doctor and geneticist about the results and your options if the screening test returns a positive result. What types of diagnostic tests are needed to confirm a positive result? Tests available will be interpreted. In addition, the implications of these findings should be discussed with experts in the condition, including a medical geneticist as well as your doctor if diagnostic testing reveals a genetic anomaly. reveals.


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