How is Down Syndrome diagnosed?

How is Down Syndrome diagnosed?

Down Syndrome is a genetic disorder caused by the presence of an extra copy of chromosome 21. It is typically characterized by certain physical features, intellectual disabilities, and developmental delays. While the condition can often be identified at birth based on physical characteristics, a definitive diagnosis is usually confirmed through medical tests.

Screening Tests

Screening tests are commonly used to identify individuals who may have a higher risk of having a baby with Down Syndrome. These tests do not provide a definitive diagnosis but help determine the likelihood of the condition. The two primary screening tests for Down Syndrome are:

• 1. Non-Invasive Prenatal Testing (NIPT): This blood test analyzes the fetal DNA present in the mother's blood. It can detect the presence of extra chromosome 21 with a high degree of accuracy. NIPT is typically performed between 10 and 13 weeks of pregnancy.


• 2. Combined First Trimester Screening: This screening involves a blood test and an ultrasound examination. The blood test measures specific proteins and hormones, while the ultrasound assesses the thickness of the back of the baby's neck (nuchal translucency). The results of both tests are combined to estimate the risk of Down Syndrome. This screening is usually done between 11 and 14 weeks of pregnancy.

Diagnostic Tests

If the screening tests indicate a higher risk of Down Syndrome, further diagnostic tests may be recommended to confirm the diagnosis. These tests provide a definitive answer but carry a slightly higher risk of complications. The two main diagnostic tests for Down Syndrome are:

• 1. Chorionic Villus Sampling (CVS): CVS involves the removal of a small sample of placental tissue for genetic analysis. This procedure is usually performed between 10 and 13 weeks of pregnancy. The sample is then examined to determine the presence of an extra chromosome 21.


• 2. Amniocentesis: Amniocentesis involves the extraction of a small amount of amniotic fluid surrounding the fetus. This fluid contains fetal cells that can be analyzed for chromosomal abnormalities. Amniocentesis is typically performed between 15 and 20 weeks of pregnancy.

Postnatal Diagnosis

If Down Syndrome is not diagnosed prenatally, it can still be identified after birth based on physical characteristics. Some common physical features associated with Down Syndrome include:

• Flattened facial features


• Small head and ears


• Upward slanting eyes


• Short neck


• Poor muscle tone


• A single crease across the palm of the hand (instead of multiple creases)

While these physical features may raise suspicion, a definitive diagnosis is typically confirmed through a blood test called karyotyping. Karyotyping involves analyzing the chromosomes to identify any abnormalities, including the presence of an extra chromosome 21.

Conclusion

Diagnosing Down Syndrome involves a combination of screening tests, diagnostic tests, and postnatal observations. Screening tests help identify individuals at higher risk, while diagnostic tests provide a definitive diagnosis. Postnatal diagnosis is based on physical characteristics and confirmed through genetic testing. It is important to consult with healthcare professionals for accurate diagnosis and appropriate support for individuals with Down Syndrome.