How to Identify Risk Factors for Down Syndrome

Baby with Down Syndrome

According to the U.S. National Down Syndrome Society, one in every 733 babies born each year has down syndrome. Down syndrome is the most commonly occurring chromosomal condition. It occurs when there are 3 copies of the 21st set of chromosomes, rather than the usual 2. For this reason, down syndrome is also referred to in the medical community as trisomy 21. Despite numerous studies, there isn't a definitive answer as to what causes the chromosomal condition, but there are a few known risk factors.

Instructions

1. Maternal Age

   One of the few known risk factors for having a child with down syndrome is maternal age. As the age of the mother increases, so does the likelihood that the child will have down syndrome. Although this is a risk, it is important to know that the majority of babies born with down syndrome each year are born to relatively young mothers.

   In fact, over 80% of babies born with down syndrome are born to mothers under age 35. This is because women of any age are at some risk and there are a lot more women under age 35 giving birth each year. The increased risk for having a child with down syndrome actually begins at age 21, as seen in the information below provided by the National Down Syndrome Society.

   Maternal Age...Risk
   20.............1 in 2000
   21.............1 in 1700
   22.............1 in 1500
   23.............1 in 1400
   24.............1 in 1300
   25.............1 in 1200
   26.............1 in 1100
   27.............1 in 1050
   28.............1 in 1000
   29.............1 in 950
   30.............1 in 900
   31.............1 in 800
   32.............1 in 720
   33.............1 in 600
   34.............1 in 450
   35.............1 in 350
   36.............1 in 300
   37.............1 in 250
   38.............1 in 200
   39.............1 in 150
   40.............1 in 100

2. 

   Heredity and Down Syndrome

   Less than 4% of all down syndrome cases are considered hereditary. There are 3 types of down syndrome non-disjunction, mosaicism, and translocation. Of these types of down syndrome, translocation is the only type that is known to be hereditary. Translocation accounts for less than 4% of all cases. Non-disjunction and mosaicism account for the remain 96% of cases and are not hereditary.

   Translocation

   If you have family member, or relative that has down syndrome, a geneticist can evaluate the chromosomal pattern to determine if it is translocation. Translocation occurs when part of the 14th chromosome breaks off during cell division and reattaches itself to the 21st pair of chromosomes.

   Nondisjunction Down Syndrome (the most common type)

   Nondisjunction accounts for 95% of cases and happens when a chromosome in the 21st set fails to separate. This extra chromosome pattern is replicated as the embryo develops. There is no definite answer as to why nondisjunction happens. Trisomies of other chromosomal pairs occur during cell division, but trisomy of the 21st pair is one of the few trisomies where the fetus survives.

   Mosaicism Down Syndrome

   Mosaicism accounts for 1% of all cases of down syndrome and occurs like nondisjunction accept the incident of having an extra chromosome in the 21 pair does not occur in all cells. Some have the typical pair instead. People with mosaicism generally have fewer health risks and developmental delays.

3. Myths About Down Syndrome

   Down syndrome is not a rare condition, occurring in 1 of every 733 live births. This statistic does not include the number of fetuses that are aborted each year because down syndrome was identified during prenatal testing.

   Although risk increases with maternal age, most children with down syndrome are not born to older parents. As stated above over 80% are born to mothers under age 35.

   Down syndrome is not attributed to smoking or drinking during pregnancy. Smoking is known to cause low birth weight, not down syndrome. Drinking is known to cause fetal alcohol syndrome, not down syndrome.

4. 

   Prenatal Diagnosis of Down Syndrome

   During pregnancy, prenatal screenings for down syndrome are available through a blood test. These blood tests are known to the medical profession as maternal serum screenings. The mother's blood is tested for markers that the fetus has down syndrome.

   Amniocentesis is usually recommended by medical professionals if the blood screening is positive, or the mother's risk is at or above 1 in 250. Amniocentesis can not be done until after the 14th week of pregnancy due to the risk of miscarriage. After the 14th week amniocentesis is known to increase the risk of miscarriage by 1/2 to 1 percent.

   Prenatal testing for down syndrome and continuation of the pregnancy is a personal choice. According to the New York Times, over 90% of women who have positive prenatal testing for down syndrome choose to abort.

   It is important to know that there are resources for women who have learned their child will be born down syndrome. There are waiting lists of parents hoping to adopt a child with down syndrome and support groups for parents choosing to raise their child with down syndrome in the resource section below.

Resources

• The National Down Syndrome Adoption Awareness Program and Waiting List to Adopt
• Email Group of Parents Waiting to Adopt a Child with Down Syndrome
• National Down Syndrome Society
• National Association for Down Syndrome
• Medical Information and Down Syndrome Resources by Len Leshin M.D., F.A.A.P and Father of a Child with Down Syndrome