An Overview of Down Syndrome

There is little knowledge and a lot of fear about Down syndrome testing, screening, and having a baby diagnosed with the syndrome. Genetic Counselor, Merlyn Glass, explains all you need to know about Down syndrome and babies born with this syndrome.

Women of advanced maternal age (35years and older) have a higher chance of having a baby with Down syndrome (DS) but many babies with DS are born to younger couples, often unexpected and thus a huge shock.

Despite having prenatal screening tests like the nuchal translucency measurement, the nasal bone measurement and the first trimester biochemical screening, with the overall risk being reduced, the only way of knowing 100% whether a baby has Down syndrome, is by invasive testing like chorionic villus sampling and amniocentesis.

Many women think that the condition is called ‘Down syndrome’ because of the slow (‘because their brains are down’) development. The syndrome is named after a physician, Dr Langdon Down, who in 1866, was the first to describe children with similar features and delayed development and named the syndrome after himself. Jerome Lejeune in 1958, discovered that Down syndrome was caused by an extra chromosome 21 in each cell of the body. The condition is therefore also known as trisomy 21.

Our bodies are made up of thousands of cells which contain the chromosomes, made up of our DNA which is responsible for not only our physical appearance, but also how we function. Individuals typically have 46 chromosomes in each cell, having received 23 copies from their mothers, and the other 23 from their fathers. When there is “mis-division” during the formation of the egg or sperm, the resultant gamete has 24 chromosomes instead of 23, therefore, after fertilization, the embryo will have 47 chromosomes instead of 46; this process is called non-disjunction. Around 95% of babies with Down syndrome will have this type of DS, but there are other types, namely mosaic DS and translocation DS which are relatively rare but have the same clinical features, and it is not possible to know which type it is just by looking at the child.

We need to be sensitive to the parents’ emotions even though they may understand the implications, complications and prognosis for a child with Down syndrome; parents don’t want their child with DS to be labelled; it is their baby FIRST, who happens to have Down syndrome not a DS baby who should be treated as any other child, but essential to be aware of the child’s limitations so as not to have unrealistic expectations. It is important not to compare their child with DS to their other children, or their friends’/families’ children; but only compare the child to him/herself; this is often reassuring to the parents, because it is natural to compare their development with typically developing children. It is very important to stress that the child with Down syndrome is expected to be delayed and allowed to develop in their own time. If a child with DS is not walking at one year, this is perfectly acceptable, and should be normalised.

Every midwife, paediatric and neonatal nurse knows how to examine a baby- and also has an innate instinctive knowledge- trust that instinct; when you have a suspicion that the baby may have Down syndrome, or another genetic condition, rather follow up, and feel reassured that the baby is indeed unaffected, or confirm that he/she does have DS, and initiate early intervention. Trust the parents; they always know when something is different about their child.

How to identify babies with Down syndrome

A baby with DS, can have some, or all of the following features:

  • A single palmar crease (simian crease)
  • Slanting eyes
  • Low set small ears,
  • Protruding tongue (due to a small mouth)
  • Incurving of the baby finger
  • Wide gap between the first and second toes, called a sandal gap

Although one may be quite clear about a clinical diagnosis for DS, a confirmation of this should be done by doing a blood test, either a full chromosome analysis or a polymerase chain reaction (PCR), which tests for the common abnormalities, trisomy 13, trisomy 18, trisomy 21 and any abnormalities of the X and Y chromosomes.

Medical- and life implications for a baby with Down syndrome

  • About 50% of children with Down syndrome have a heart defect and may have to be on medication, and others may need corrective surgery.
  • Having low thyroid hormones is also a common finding in children with DS, and at the same time as doing the blood for chromosomes, it is advisable to do a thyroid function. Thyroid function should be tested at birth, at 6 months, at one year and then annually thereafter. Low thyroid is easy to treat, and the baby should be referred to an endocrinologist for treatment.
  • Because all children with DS will have low tone and developmental delay, not often obvious for the first few months, it is important that they be referred to a physiotherapist and/or occupational therapist for an assessment and management.
  • They will also need a hearing test within the first month, and referral to speech therapy thereafter. A hearing assessment should be done annually thereafter.
  • All babies with DS should have a full blood count within the first month of age, and thereafter, an annual haemoglobin check.
  • An ophthalmological assessment is also important; some children with DS may have cataracts which will need to be diagnosed and treated early. They also may have visual problems, like short sightedness due to the laxity of all muscles and will need glasses.
  • As the child becomes older, it is important to address sexuality and relationships. Individuals with DS have the same needs as everyone; to be loved, to develop self-esteem, be proud of themselves and to have meaningful relationships.

This is all very overwhelming for new parents, and as compassionate and empathic as the professionals can be, it is helpful to refer the family to the Down syndrome support group. The group comprises parents who have experienced the early feelings of shock and perhaps disappointment, the longing, the sadness about having a baby with DS, and often the chronic grief. Other parents understand the sorrow that parents experience, not only about the loss of their dream of having a “normal” baby, but also every time there is another reminder that their child is different; the delayed milestones, the special schools, that their child will never “matriculate”, drive a car, and perhaps never get married or have children.

Ideally, every pregnant woman should be offered the option of early screening, and if found to be at higher risk, offered the option of invasive testing. Many women are not fully informed of the pros, cons and risks of all the testing. It is important that any couple or woman who enquires or is at higher risk of having a baby with Down syndrome, or any other inherited condition, should be fully counselled, either by a midwife or their doctor, and ideally be referred to a genetic counsellor so that she and her partner can make informed choices around their pregnancy. With a subsequent pregnancy, couples are often anxious, and feel guilty about wanting prenatal testing. These issues must be sensitively discussed before they make any decisions.

Contact numbers for Genetic Counselling

NHLS/WITS: 011 4899223 / 4

UCT: 021 406 6698 / 6995

STELLENBOSCH: 021-938-9807 / 9787