What are Down syndrome and trisomy 18?
These chromosome abnormalities are caused by having an extra copy of either chromosome #21 (Down syndrome) or #18 (trisomy 18) in every cell of the developing baby. The extra chromosome contains many genes. This excess genetic material causes mental retardation and may also cause birth defects. The common forms of Down syndrome and trisomy 18 are usually not inherited and therefore may not be seen in families. The chance for any woman to have a baby with an extra chromosome increases with age.
Related Questions
- Are women who screen positive for Down syndrome, trisomy 18, or ONTDs in a previous pregnancy eligible for an amniocentesis in their current pregnancy?
- Do the results of prenatal screening provide information other than risk for Down syndrome, trisomy 18 and open neural tube defects?
- Do the results of serum screening provide information other than risk for Down syndrome, trisomy 18 and open neural tube defects?
