Down syndrome is a genetic condition that occurs when a baby is born with 47 instead of 46 chromosomes. This condition is first described in 1866 and named after its founder Dr John Langdon Down. The real cause of this condition was discovered in 1959, when Dr Jérôme Lejeune identified it as a condition that occurs when there is an extra chromosome 21, instead of normal two. Therefore, the condition became known as trisomy 21 (having three chromosomes instead of a pair). Down syndrome sometimes occurs as a whole trisomy 21, or as a result of genetic translocations. Whatever is the case, this condition is caused by the presence of an extra copy of genetic material, and it affects patients in many different ways. In most cases, these babies are born with mild to severe health problems, typical facial features, developmental delay and mental retardation.
Down syndrome statistics
Down syndrome affects about one per every 733 live births. Maternal age plays an important role in overall risks of having a baby with Down syndrome. The risk factors are increasing with age because older eggs have a greater risk of improper chromosome division. Therefore, women younger than 35 have 1/400 chances of conceiving a child with Down syndrome. By age of 45, the risk is 1/35. However, 80% of children with Down syndrome are born to women under the age of 35. This is a result of the overall fertility of younger women.
Down syndrome in the United States
The incidence of Down syndrome in the United States is not steady and the total number of cases has increased by 24.2% from 1979-1983 to 1999-2003. The lowest prevalence of Down syndrome at birth was found in Arkansas, with 9.7 births per 10,000 live births, while the Utah has the highest rates with 13.7 cases per 10,000 live births.
Again, the maternal age seems to play a significant role among all risk factors. A number of babies born with Down syndrome was found to be about five times higher among births to older mothers, than among births to younger ones. For example, older mothers delivered 38.6 affected babies per 10,000 live births, while younger mother delivered only 7.8 per 10,000.
It is estimated that about 83,000 children and adolescents living in the United States suffer from Down syndrome. The lowest prevalence is found among Non-Hispanic black race and ethnic groups, while the Hispanic individuals have the highest prevalence, followed by Non-Hispanic white individuals and all other races and ethnicities.