FAQs on Down Syndrome - part 2
Down syndrome remains the most common chromosomal condition diagnosed in the United States. Each year, about 6,000 babies born in the United States have Down syndrome. This means that Down syndrome occurs in about 1 in every 700 babies.
All 3 types of Down syndrome are genetic conditions, but only 1% of all cases of Down syndrome have a hereditary component (passed from parent to child through the genes).
Once a woman has given birth to a baby with trisomy 21 or translocation, it is estimated that her chances of having another baby with trisomy 21 is 1 in 100 up until age 40.
The extra chromosome 21 leads to the physical features and developmental challenges that can occur among people with Down syndrome. 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. Women who are 35 years or older when they become pregnant are more likely to have a pregnancy affected by Down syndrome than women who become pregnant at a younger age. However, the majority of babies with Down syndrome are born to mothers less than 35 years old, because there are many more births among younger women.