Having a baby with Down syndrome can happen to anyone. The cause of Down syndrome is unknown, but it has been found that women over age 35 have a slightly higher risk of having a baby with Down syndrome. However, the majority of babies with Down syndrome are born to mothers under 35 years old because of the high number of pregnancies in this age group.
As most of you are aware, women are born with a set number of eggs in their ovaries. Cell division in those eggs remains suspended in each, until shortly after ovulation. It is possible that as eggs age and remain suspended in their cell division for many years, something happens to cause the chromosomes in them to become sticky or to fail to separate properly. Research has supported the view that older eggs are more prone to errors in cell division with increasing maternal age.