The prevalence of infants that are being born with Down syndrome has increased at a dramatic rate in recent years. Scientists have said that the prevalence of live born infants with Down syndrome increased by approximately 31 percent between the years 1979 and 2003, and from 9 to 11.8 percent per 10,000 live births in the 10 U.S. regions that were studied.
This study shows that the numbers represent an average increase of approximately 0.9 percent annually. The researchers analyzed the data from 10 population-based birth registries in the United States, which estimates the prevalence at birth among children up to age 19 in each region, and also in all of the areas added together.
During the studied periods, the prevalence at birth significantly increased among the infants born to older mothers and was decreased slightly among the births to younger mothers. Maternal age of 35 and older has been a known risk factor for having a child with Down syndrome, which is the most common chromosomal disorder.
Down syndrome is caused by an abnormal cell division that occurs in early fetal development. The medical experts believe that it often starts in a the egg prior to or at the time of conception. Less often, the error occurs in the sperm at the time of conception. However, it is still not known what exactly causes the cells to divide abnormally.
Genes are grouped together to make up our chromosomes. Normally, a child would inherit 46 chromosomes, 23 from each parent. The abnormal cell division that is related to Down syndrome produces extra genetic material, an extra chromosome. Down syndrome is usually classified according to the specific way that the extra genetic material is produced. Translocation-type Down syndrome can sometimes be passed down through families (inherited).
The researchers wrote, “The overall [Down syndrome] prevalence at birth was almost five times higher among births to older mothers (38.6 per 10,000) than among births to younger mothers (7.8 per 10,000).”
This new study also shows that:
- The prevalence of Down syndrome at birth was consistently higher among the non-Hispanic whites than among the non-Hispanic blacks.
- The prevalence of Down syndrome was also consistently higher among males than females, regardless of age group, race, or ethnicity.
- In the year 2002, Down syndrome was present in approximately one of every 971 children and adolescents up to the age of 19 that were living in the 10 regions studied.
“Our study also confirmed an increase in prevalence in [Down syndrome] at birth over time, and this trend over time paralleled the increasing proportion of births to older mothers,” the researchers stated.
The researchers said that their findings could reflect an increasing proportion of births to older mothers, and the improvements shown in the survival rate of the infants with the genetic disorder. People that suffer from Down syndrome are at a higher risk for medical problems such as hearing and vision problems, respiratory problems, and defects of the heart.
The researchers noted that the number of children, adolescents, and adults that have Down syndrome is likely to increase and the people that have the condition are likely to live longer. The authors said in a news release that their findings might be useful in helping determine the number of people with Down syndrome and assist in the development of new policies to help them.