Down syndrome is a genetic disorder that leads to several physical and mental disabilities. It occurs due to the presence of an extra chromosome 21 referred as trisomy of chromosome 21. Down syndrome seems to occur more among males than females.
Overall, the two sexes are affected roughly equally. The male-to-female ratio is slightly higher (approximately 1.15:1) in newborns with Down syndrome, but this effect is restricted to neonates with free trisomy 21.
Both men and women can pass the genetic translocation for Down syndrome on to their children. Having had one child with Down syndrome. Parents who have one child with Down syndrome and parents who have a translocation themselves are at an increased risk of having another child with Down syndrome.
It is well known that the extra chromosome 21 originates from the mother in more than 90% of cases, the incidence increases with maternal age and there is a high recurrence in young women.
Risk for chromosome problems
The chance of having a child with Down syndrome increases over time. The risk is about 1 in 1,250 for a woman who conceives at age 25. It increases to about 1 in 100 for a woman who conceives at age 40. The risks may be higher.
Parents with one baby with regular trisomy 21 are usually told that the chance of having another baby with Down's syndrome is 1 in 100. Very few families are known who have more than one child with Down's syndrome, so the real chance is probably less than this.
A recent study suggests that a 20-year-old father doubles the chance of Down syndrome as compared to one who's 40.
You can't prevent Down syndrome since it's a genetic condition. To learn more about your risk of having a child with a genetic condition, talk to your healthcare provider about genetic testing.
Causes and Risk Factors
Researchers know that Down syndrome is caused by an extra chromosome, but no one knows for sure why Down syndrome occurs or how many different factors play a role. One factor that increases the risk for having a baby with Down syndrome is the mother's age.
Most individuals with Down syndrome have mild (IQ: 50–69) or moderate (IQ: 35–50) intellectual disability with some cases having severe (IQ: 20–35) difficulties. Those with mosaic Down syndrome typically have IQ scores 10–30 points higher than that.
In almost all cases, Down's syndrome does not run in families. Your chance of having a baby with Down's syndrome increases as you get older, but anyone can have a baby with Down's syndrome. Speak to a GP if you want to find out more.
People with Down syndrome can expect to live to 60
In the 1940s, a child with Down syndrome had a life expectancy of 12 years. These days, their life expectancy is 60 years and a baby born with Down syndrome could live into their 80s — in line with the general population.
In a sample of 75 children with trisomy for chromosome 21, or Down syndrome, there were 42 males and 33 females. The sex ratio was 1.30 which is statistically not significant (p greater than 0.05).
RESULTS: The odds ratio and population attributable risk of Down syndrome due to maternal age of 35 years or older were highest for Mexican Americans, intermediate for African Americans, and lowest for non-Hispanic Whites.
During 2014-2018 (average) in Tennessee, was highest for Hispanic infants (22.8 in 10,000 live births), followed by Asians (15.1 in 10,000 live births), Whites (13.8 in 10,000 live births) and blacks (10.8 in 10,000 live births).
Down syndrome, which arises from a chromosome defect, is likely to have a direct link with the increase in stress levels seen in couples during the time of conception, say Surekha Ramachandran, founder of Down Syndrome Federation of India, who has been studying about the same ever since her daughter was diagnosed with ...
Down syndrome occurs in people of all races and economic levels. The risk increases with the mother's age (1 in 1250 for a 25 year old mother to 1 in 1000 at age 31, 1 in 400 at age 35, and about 1 in 100 at age 40). However, 80% of babies with Down syndrome are born to women under age 35 years.
Current supplementation policies designed to prevent neural tube defects may incidentally prevent Down's syndrome, provided a sufficiently high dose of folic acid is used.
Because the likelihood that an egg will contain an extra copy of chromosome 21 increases significantly as a woman ages, older women are much more likely than younger women to give birth to an infant with Down syndrome.
Inheritance. Most cases of Down syndrome are not inherited. When the condition is caused by trisomy 21, the chromosomal abnormality occurs as a random event during the formation of reproductive cells in a parent. The abnormality usually occurs in egg cells, but it occasionally occurs in sperm cells.
One in every 691 babies in the U.S. is born with Down syndrome, making it the most common chromosomal condition. There are more than 400,000 people living with Down syndrome in the U.S. In 1983, the average life expectancy of a person with Down syndrome was a mere 25-years-old. Today, it's 60.
Down syndrome incidence in humans increases dramatically with maternal age. This is mainly the result of increased meiotic errors, but factors such as differences in abortion rate may play a role as well.