What Causes Down Syndrome in Babies
What is Down Syndrome?
Down Syndrome (DS) is a genetic aberration where a baby is born with an extra copy of the chromosome 21. All of us usually have 2 copies of each chromosome but in the case of Down syndrome the baby gets an extra copy of number 21 chromosome, hence the other name Trisomy (3 copies) 21. How this condition affects varies widely from baby to baby based on the severity. Early intervention, treatment and support could help many kids with Down Syndrome lead fulfilling lives.
Down Syndrome Causes
In many if not most cases Down Syndrome is not inherited meaning it is not something that you or your partner did or are responsible for but the risk factors increase with age especially in women above 35 and men above 40.
Most of us have 23 pairs or 46 chromosomes in each cell of our body where we inherit 23 from our mother and 23 from our father. In the case of Down syndrome they also have an extra copy of the number 21 chromosome. Based on how this extra chromosome appears in the cells of the body Down Syndrome is classified into three categories
Trisomy 21: When all the cells of the body have 3 copies of chromosome 21 it is a trisomy. It is most common form of of Down Syndrome affecting 95% of the cases.
Translocation Down Syndrome: Occurs when a part of or the whole copy of chromosome 21 is found attached, hence translocated to another chromosome. It happens in only 3% cases of babies with Down Syndrome.
Mosaic Down Syndrome: Happens when some of the cells have the usual 2 copies of chromosome 21 like all of us but the others have 3 copies of the chromosome 21. This occurs in just 2% of the cases with Down Syndrome. As this has only some cells in the body affected, it usually shows the least symptoms compared to other forms.
Related: Congenital Heart Defects
Down Syndrome Symptoms
Down syndrome affects both physical and mental development of the body but the extent to which it does varies greatly from baby to baby. Some grow up to lead fairly independent lives while some may need a lot of support and care. Some of the possible symptoms include:
Physical Appearance:
A flat nose
Almond shaped eyes that slant upward at outer corner
White spots in the eye
Short neck, small hands and feet
Weak muscle tone and joints
Palmer Crease: A single crease along the palm
Short stature
Tongue sticking out
Pinky finger curved in and small in size
Mental Development:
Most kids have mild to moderate intellectual difficulties like thought, reasoning or comprehending things. They may reach milestones later than others and may take longer to learn new skills but with right tools, timely intervention and support most of them do well.
Health Conditions:
Many kids with Down Syndrome are more prone to certain health issues than the others. Some may have mild to no medical conditions at all while the others may need life long medical care. Some of the common health conditions seen in Down Syndrome are:
Heart Defects - About half of all kids with DS have heart issues, so it is very important to have them checked
Vision and Hearing Problems - Many with DS also have issues with vision and hearing, they need to be checked from time to time
Speech Difficulties - Many have speech delays or difficulties associated with the hearing and vision issues and need to be checked to ensure they get the timely help
They are also prone to Thyroid issues, Intestinal problems, Seizures, Ear infections, Asthma, Sleep apnoea, Leukaemia, Pneumonia, Obesity, Alzheimer, Neck and Spinal issues.
Down Syndrome Diagnosis
Many cases are diagnosed during pregnancy when women undergo blood tests, ultrasound to make sure everything is good with you and the baby. During these routine tests if the doctor suspects any issues may suggest few other invasive tests. Some of the tests and procedures done during pregnancy that confirm Down Syndrome are:
Blood Tests:
During the first trimester your doctor will check the levels of PAPP-A protein and HCG hormone in your blood. Any out of the normal range could signal a problem with the baby and reason to probe further.
During the second trimester your doctor will ask for maternal serum triple or quad screening test to look for levels of 3 to 4 substances in the blood like AFP protein, HCG hormone, Estriol if triple test and hormone inhibitor A as well if quad test. The unusual level are usually an indicative of your baby having DS or other genetic issues but need further tests to be a 100% certain.
Non-Invasive Prenatal Testing or Cell Free DNA Screening Test:
This test looks for any unusual number of chromosomes in the mothers blood where baby's DNA is now circulating after passing through the placenta. This test is usually very accurate in predicting Down Syndrome and few other genetic conditions.
Nuchal Translucency Scan
It is an ultrasound scan where your doctor will look at the back of the baby's neck for nuchal fold as it is filled with extra fluid in case of DS and few other genetic conditions. It is looked at in combination with the blood test for Down Syndrome.
While most of the above tests are pretty accurate, they are not a 100% certain and so your doctor would recommend you do a few other diagnostic tests to confirm Down's syndrome if the above tests come positive. The below tests are not risk free and hence should only be done if your doctor advises you to do so.
Chorionic Villus Sampling Test (CVS)
Chorionic Villi are tiny finger like projections of the placenta that have same genetic material as your baby, cells from the chorionic villi will be extracted using a needle to test for any abnormalities. This test would be suggested during the first trimester at 10th to 12 weeks of pregnancy if the blood tests and ultrasound have shown to be positive for Down Syndrome.
Amniocentesis
Can be done during the second or third trimester where a slender long needle is inserted through your stomach to get a sample of the amniotic fluid which is then tested for genetic conditions like Down Syndrome.
Percutaneous Umbilical Blood Sampling Test (PUBS)
This test is also done during the second trimester where a needle is inserted into your umbilical cord to draw blood to test for the genetic issues like Down Syndrome. This is not as commonly used as the other two.
Tests to confirm Down Syndrome after birth:
Physical Exam: Doctors look for physical signs and appearance but sometimes babies without Down Syndrome may also have similar physical characteristics and may need blood test to rule out the suspicion.
Chromosomal Karyotype: A blood sample is drawn from the baby after birth to assess all the chromosomes of an individual cells and spot the chromosomal abnormalities like Trisomy 21 to confirm Down Syndrome.
Down Syndrome Treatment
There is no cure for Down Syndrome but there are treatment options to help your child reach their full potential both physically and mentally.
Therapy: You can take help of physical, speech and occupational therapy to help your child with sitting, walking, communication and day to day life skills
Behavioural Counselling: Many kids with DS also have behavioural issues, temper tantrums, ADHD, autism or compulsive behaviour that needs help managing.
Support System at Home: Work with the therapists and counsellors to create a routine and a positive environment at home that helps your child learn new skills. Communicate with your kid in small clear sentences that are easy to follow. You can also use picture or songs to teach them things. Ask them to repeat to make sure they understand what you said. Many kids with DS do decently well at day to day activities, they may take a little longer to learn but that shouldn't deter you as with little patience and lots of love they will come a long way.
Long term Prognosis of Down Syndrome
Long term prognosis is good for individuals with mild to moderate DS, they can comprehend, communicate and lead a fairly independent life. Th life expectancy is up from 25 in 1980's to 60 years now, some even go on to live to 70s and 80s. Timely intervention, robust support system at home and a positive approach toward working with your child is the key.