Although the main causative aspect for Down syndrome is genetic, a number of findings suggest that some other factors may also be contributory to the development of the abnormality. It is vital to know about these to stay safe. Early detection and consistency in the prevention and treatment approaches can help a lot in alleviating the problem.
About Types and Causes
Normal human cells have 23 pairs of chromosomes. A chromosome in every pair stems from the father, while the other comes from the mother. There are 3 types of abnormal cell division that involves he 21st chromosome. The cause of Down syndrome is considered to be one of the three types. All three abnormal divisions lead to the extra genetic material from chromosome 21, which is functional for the unique features and developmental problems that is Down syndrome.
In the case of Trisomy 21, the condition is caused by abnormal cell division that occurs while the sperm cell or egg cell is still developing. Patients with trisomy 21 have 3 copies of the chromosome 21 instead of the regular 2. The Mosaic type is rare, caused by the abnormal cell division after fertilization. Kids in this case, have cells with an extra copy of chromosome 21. Translocation type has the regular 2 copies of the chromosome 21, as well as additional material from chromosome 21 attached to the chromosome being translocated. This occurs before or during conception. Environmental and behavioral factors are not known to cause Down syndrome.
Majority of Down syndrome are actually not inherited. There are mistakes that occur during cell division as the egg, embryo or sperm develops. The translocation Down syndrome is the only type that can be passed from the parents to the kids. Only around 4% of Down syndrome patients have the translocation type. Around 50% of the cases are inherited from either parent. During the occurrences, the father or the mother is a balanced carrier of the translocation, meaning that he or she has a kind of rearranged genetic material, with no extra genetic material. A balanced carrier displays no sign or symptom of the condition, although the translocation can be passed on to the children.
The possibility of passing on the translocation type will depend on the gender of the parent that has the rearranged chromosome 21. There is a risk of around 3% if the father is the carrier. There is a 12% risk if the mother is the carrier.
On Maternal Age
Most cases of Down syndrome is caused by a random event during the formation of reproductive cells, the sperm or ovum. The incidence of Down syndrome actually grows as the mother grows older or with increasing maternal age. Not all parents with translocation trisomy 21 actually are balanced carriers. There may be zero risk in future pregnancies. As mothers grow older, the possibility of errors will grow as close as having a ratio of 1:12 when they reach 45 years old.
Several experts recommend that pregnant women age 35 years old or older should undergo prenatal tests and diagnostic procedures to find the possibility of Down syndrome. Using maternal age alone does not detect more than 75% of pregnancies that lead to Down syndrome. It is important that women consider their age as a factor to determine the cause of the problem.