The risk for Down Syndrome is different for each pregnancy, as it depends on a number of risk factors. Risk factors can include a variety of things, however, family history and age are two of the leading items that can add to the overall risk. Here are details on how these two aspects contribute to the risk of Down Syndrome.
Family History
There are three types of Down Syndrome: trisomy 21, mosaicism, and translocation. Trisomy 21 is the most common type and occurs when three, rather than two, copies of chromosome 21 are inherited by the fetus from the parents. The second type, mosaicism, happens when some of the fetus’ cells get three copies of chromosome 21, while others get the standard two copies. There is only one type of Down Syndrome that is passed down genetically: the third type, called translocation. With translocation Down syndrome, a piece of one chromosome 21 breaks off and attaches itself to another chromosome. Four percent of people with Down Syndrome have this type.
There is a higher probability of being a carrier (someone who inherited the genetic trait of a disease but does not suffer from it) of the translocation type of Down Syndrome if there is a family history of Down Syndrome or if a mother has had other children with translocation Down Syndrome. If you believe you may be a carrier, an obstetrician can recommend a genetic carrier screening.
Age
For women who become pregnant at an advanced age, there are higher rates of pregnancy complications, such as preeclampsia, gestational diabetes, and miscarriage. Many women over the age of 35 have healthy pregnancies and give birth to healthy babies. However, maternal age does increase the risk of issues arising.
Genetic disorders are a potential concern for expecting mothers who are 35 years of age or older. Women are born with all their eggs in their ovaries, and with older eggs comes a higher risk of improper cell division after fertilization. This risk increases starting at age 35 and rises as a woman ages. The risk of the developing baby having Down Syndrome is about:
1 in 1,200 in women age 25.
1 in 350 in women age 35.
1 in 100 in women age 40.
1 in 10 in women age 49.
A Healthy Pregnancy
There is no way to prevent Down Syndrome. If there is a family history of Down Syndrome or if a mother is over the age of 35, doctors will keep a close watch on a pregnancy and inform patients of all of the options available along the way. Neither advanced age nor family history ensures the presence of a chromosomal abnormality. These things just increase the potential risk. If you are concerned about the presence of a chromosomal abnormality in your pregnancy, consult a physician and/or genetic counselor to evaluate what your next steps should be.
