ABSTRACT
Down syndrome is the most common identifiable genetic cause of intellectual disability with an incidence of approximately 1 in 800 live births. It is more com mon in older mothers but, as the majority of babies are born to younger women, most mothers of babies with Down syndrome are aged in their twenties. Despite a growing trend for women to have children later in life, the annual rate of Down syndrome births in the West is fairly constant. This is due to advances in prenatal screening leading to the termination of many affected pregnancies.
