Maternal Age Plays a Key Role in Regulating Down Syndrome

Written by Shefin B for Biomed Middle East

It’s a striking finding, considering that more women are waiting longer to have children – a factor that increases the chances of Down Syndrome. Since Down syndrome is a Chromosomal Disorder caused by an error in cell division, the likelihood of such an error occurring increases with maternal age. This means that an older mother is likely to give birth to a child with Down syndrome than her younger counterpart.

According to the National Association for Down syndrome, “80% of babies born with Down syndrome are born to women younger than 35. The average maternal age is 28 years old.”The likelihood of a woman under 30 years of age giving birth to a child with Down Syndrome is less than 1:1000, but increases the older the women gets, with an incidence of about 1:112 at 40 years of age.

Down syndrome (Trisomy 21) is a chromosomal disorder caused by the presence of all or part of an extra 21st chromosome. The presence of extra set of genes leads to overexpression of the involved genes, leading to the increased production of certain products.
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It is named after John Langdon Down, the British physician who described the syndrome. Down syndrome occurs in all human populations.

Human cells normally have 46 chromosomes which can be arranged in 23 pairs. Of these 23, 22 are alike in males and females; these are called autosomes. The 23rd pair are the sex chromosomes. If a sperm or egg with an abnormal number of chromosome merges with a normal mate, the resulting fertilized egg will have an abnormal number of chromosomes.

In Down syndrome, 95% of all cases are caused by this event: one cell has two 21st chromosomes instead of one; so the resulting fertilized egg has three 21st chromosomes. Hence the scientific name 21st trisomy

Problems faced

People with Down syndrome may be born with a variety of birth defects. About half of all affected children have a heart defect. Individuals with Down syndrome have an increased risk of developing several medicinal conditions. These include gastroesophageal reflux, which is a backflow of acidic stomach contents into the esophagus, and celiac disease, which is an intolerance of a wheat protein called gluten. About 15 percent of the people with Down syndrome have an underactive thyroid gland. Individuals with Down syndrome also have an increased risk of haring and vision. Additionally, about 1 percent of children with Down syndrome develop leukemia.

Adults with Down syndrome have an increased risk of developing Alzheimer disease, a brain disorder that results in a gradual loss of memory, judgment, and ability to function. Although Alzheimer disease is usually a disorder that occurs in older adults, about half of adults with Down syndrome develop this condition by age 50.

Diagnosis: During the second trimester of pregnancy, serum alpha-feto protein(AFP) is commonly used for evaluating the risk of Down syndrome. Decreased levels of AFP are indicative of Down syndrome. Petit etal, from France reported that congenital deficiency of AFP may result in decreased AFP in the maternal serum and amniotic fluid. They also reported that a male fetus with congenital absence of AFP, due to truncating mutation , who showed normal growth and development.

Down syndrome is usually identified at birth by the presence of certain physical traits: low muscle tone, a single deep crease across the palm of the hand, a slightly flattened facial profile and upward slant to the eyes.

Down syndrome and maternal age: Researchers have established that the likelihood that a reproductive cell will contain an extra copy of chromosome 21 increases dramatically as woman ages. Therefore, an older mother is more likely than a younger mother to have a baby with Down syndrome.

The incidence of Down syndrome rises with increasing maternal age. Many specialists recommend that women who become pregnant at age 35 or older undergo prenatal testing for Down syndrome. The likelihood that a woman under 30 who becomes pregnant will have a baby with Down syndrome is less than 1 in 1,000, but the chance of having a baby with down syndrome increases to 1 in 400 for women who become pregnant at age 35. But using maternal age alone will not detect over 75% of pregnancies that will result in Down syndrome.

Future of Down Syndrome

Recently it has been reported that children with Down syndrome might benefit from medical intervention that includes amino acid supplements and a drug known as Piracetam. Piracetam is a physhoactive drug that some believe may
Improve cognitive function. However there have been no controlled clinical studies conducted to date using Piracetam to treat Down syndrome.

Also scientist at the National Institute of Child Health and Human Development reported that studying mice models at varying stages of development will enhance our basic understanding of Down Syndrome and facilitate the development of effective interventions and treatment strategies.