What is the chance that my baby will have Down syndrome? If you're asking the question, you're probably pregnant or considering pregnancy.
Most people have seen a child with Down syndrome - it's fairly easily to recognize. What people fear isn't so much the physical problems these children exhibit, but the mental retardation caused by the extra chromosome #21.
The incidence of Down syndrome increases with the age of the mother. Although alcohol and tobacco use have been linked to other conditions, they are not thought to increase the risk of Down syndrome. According to the Merck Manual, a time-honored medical reference, the overall risk is 1 in 800. However, for babies born to 20-year-old mothers the risk is only 1 in 2000 births. By age 35 the risk rises to 1/365, and at age 40 is about 1%.
The answer is a bit more complicated than this, however, because not all Down syndrome has the same genetic cause. Most cases (about 95%) are due to a second copy of a complete chromosome 21. The other 5% of cases are due to an extra fragment of chromosome 21 getting stuck on a different chromosome (called a translocation).
The genetic cause can be determined by examining the chromosomes of the child and/or parents. If the mother carries a translocation, the risk for having a child with Down syndrome is about 1 in 10. If the father carries the abnormal chromosome, the risk is about 1 in 20. Chromosome testing would not normally be performed on parents unless they've already had one child with Down syndrome.
Pregnant women can be tested to see if their baby is likely to have Down syndrome, but this testing may or may not be covered by your insurance. Because testing is expensive (hundreds of dollars), not entirely accurate, and potentially dangerous to the unborn child, you should talk to your doctor about reasons to perform the test and reasons not to.
No comments:
Post a Comment