Types of down Syndrome, Risk Factors and Diagnosis

There are diverse forms of Down syndrome that have been recognized and documented. Understanding these types has been facilitated by the advancement in the study of genetics. Moreover, persons suffering from this condition are at risk of contracting various other diseases. This means that they spend the rest of their lives struggling with the diseases. If not managed, the victims could succumb to these diseases. This article will give an insight into the types of Down syndrome, the risk factors associated with the condition and how a pregnant mother is diagnosed.

Trisomy 21

Also known as non-disjunction, it constitutes 90-95% of all the Down syndrome incidences that occur. The condition a genetic disorder but trisomy 21 is not hereditary. This simply means that kids born from parents with this genetic condition do not necessarily suffer from the condition. Its occurrence is based on the failure of 2 of the mother’s 21 chromosomes to fully separate. Once this occurs, these chromosomes are then integrated into the sperm or even the mother’s egg. This gives it the non-disjoint name. Once the egg is fertilized the 47 chromosomes are formed and replicated into every body cell of the foetus.


This is another form of Down syndrome that constitutes at least 1% of all the documented cases of Down syndrome. Unlike trisomy 21, mosaicism is rare. Its occurrence is based on the replication of the additional chromosome into a number of the body cells when the foetal cells begin to divide. This creates a case where some cells are normal while others have the extra chromosome. Essentially, the persons suffering from this kind of Down syndrome show partial characteristics of the same with less partial features and symptoms. The condition can also arise from the non-disjunction which occurs a short while after fertilization. Thereafter, a mosaic of normal and abnormal cells from where some cells contain 46 chromosomes while others contain 47 chromosomes.

Robertsonian translocation

Robertsonian translocation

Another type of Down syndrome condition is the Robertsonian translocation characterized by the infusion of part of the 21 chromosomes with chromosome 14 or at times other chromosomes. The condition leads to the development of cells with a normal number of chromosomes but one of the cells contains an extra genes set that originates from the attached replica of chromosome 21. Mostly, patients suffering from this type of condition take up approximately 4% of the total number of documented cases. Children born from a person with this kind of condition can inherit the genes. This makes the condition hereditary unlike the other 2 types of Down syndrome.

Risk Factors

Generally, Down syndrome is associated with a number of conditions that if not taken care of can be life-threatening. Most of these conditions can affect any body system or any organ which means that they should always be kept in check. Usually, almost half of all the victims of Down syndrome suffer from a heart flaw. Additionally, the victims of this conditions are at a high risk of suffering from thyroid conditions, epilepsy, childhood leukaemia, Alzheimer’s disease, hearing difficulties and respiratory problems. A few cases of cancer, diabetic retinopathy and artery hardening have been documented in a number of victims suffering from Down syndrome.


A number of tests are carried out on women with a higher chance of getting children with this condition. Diagnosis may involve screening of the pregnant mother. This test shows the probability of the foetus to be suffering from this condition. Other tests give exact results on whether or not the foetus is suffering from Down syndrome. Due to the fact that the risk of women to conceive a child with such a condition increase as one age, genetic screening of pregnant women between 30 to 35 years is done. It can be done through genetic ultrasound, cell-free DNA, integrated screening, quadruple or triple screening, and nuchal translucency testing. Moreover, diagnostic tests can be carried out. These include percutaneous umbilical blood sampling, amniocentesis and chorionic villus sampling.


Down syndrome is not a condition that should be ignored. It calls for either screening or diagnosis of the mother before birth to establish if the foetus is suffering from the condition. Therefore, pregnant mothers should visit the doctors to establish the appropriate measure to take. Once it is established that the child is suffering from one of the three types of Down syndrome, care should be taken to protect them from the life-threatening risk factors and give the kid a long and productive life.