Down Syndrome – What is it?
Down syndrome is the most common inherited-chromosomal disorder, affecting an estimated 1 baby in 700 live births. It is also the most common cause of learning difficulties in children.
How does it occur?
Genes that make up who we are, are composed of threads of DNA called chromosomes. A baby is usually born with 23 pairs of chromosomes. Down syndrome is a genetic condition in which the baby is born with an extra copy of chromosome 21, which is why it is also known as Trisomy 21.
What are the risk factors for Down Syndrome?
- Advancing maternal age: There are some recognised risk factors for Down Syndrome, among which advancing maternal age is the most substantial (94%).Older mothers (≥ 35 years) have an increased risk of having babies with Down Syndrome, with the risk increasing with increasing age. However, due to the fact that older women have fewer pregnancies; most affected babies are born to younger mothers.
- Genetic factors: Genetic translocations can cause Down Syndrome up to 5% of the time.
Symptoms of Down Syndrome?
Down Syndrome babies have characteristic faces and features. Some of the features seen are:
- A flat face
- A depressed nasal bridge
- Eyes that slant upwards, also known as a Mongoloid slant
- A small mouth with a protruding tongue
- Small ears
- A short neck with redundant skin on the back of the neck
- A single line or crease across the palm
- Short fingers with inward curvatures of the little finger
- A pronounced ‘sandal’ gap between the big toe and second toe
- Poor muscle tone or floppiness; with hyperflexible joints
- Tiny white spots in the eye also called Brushfield spots.
What other problems can a baby with Down Syndrome have?
Babies and children with Down Syndrome have an increased risk of other medical problems, such as:
- Congenital heart defects ( ~50%)
- Intestinal problems, which may require surgical treatment
- Delayed motor development
- Learning difficulties – usually mild to moderate, but may be severe
- Increased risk of infections
- Increased risk of thyroid problems
- Increased risk of blood cancer and other tumours
- Vision problems like refractive errors, Cataract and Squint
- Obstructive sleep apnoea, a condition where breathing stops temporarily during sleep (50-75% cases)
- Hearing loss
- Short stature
- Hip dislocation
- Early-onset Alzheimer’s disease
Down syndrome and pregnancy
Two types of screening tests are done to detect Down Syndrome during pregnancy:
- Non-Invasive Prenatal Testing (NIPT): This is a blood test that measures biochemical markers in the mother’s blood. It is termed non-invasive because it only requires blood drawn from the mother and is safe for the baby.
- Nuchal translucency (NT) Scan: This is an ultrasound scan which assesses the clear fluid or space at the nape of the baby’s neck between 11 and 14 weeks of pregnancy.
All pregnant women are now offered screening tests; however, these tests do not give a concrete diagnosis.
How is Down Syndrome diagnosed?
In case of a positive screening test, the following types of diagnostic tests can be done to confirm the presence of Down Syndrome:
- Chorionic Villous Sampling (CVS): Checks cells from the placenta, done between 10 and 13 weeks of pregnancy.
- Amniocentesis: Examines cells from the amniotic fluid or the fluid that surrounds the baby in the womb, usually done between 15 and 20 weeks of pregnancy.
- PUBS – Percutaneous Umbilical Blood Sampling: Here, the blood sample is taken from the umbilical cord. It gives the most accurate diagnosis of Down syndrome during pregnancy, done between the 18th and 22nd week.
These tests involve checking the sample taken for the extra chromosome 21, and results can take up to 2 weeks.
Prenatal diagnostic testing is invasive and involves some risk to the mother and unborn baby, including a risk of miscarriage.
Cure for Down Syndrome
Down Syndrome is a lifelong genetic condition that has no cure. Down Syndrome babies are like other babies but have characteristic features and may require help with some activities, like feeding. They may also require treatment for the other problems that may be part of the syndrome.
They require multidisciplinary care with physical, speech, occupational and educational therapies to improve their skills; these are ideally started as part of early intervention programs. The quality and expectancy of life of people with Down Syndrome have increased dramatically over the years , with many children living fulfilled and enriched lives into adult years.
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