A PREGNANT woman who knows her unborn child has Down’s syndrome might one day be able to prevent some symptoms before giving birth.

That at least is the hope raised by experiments in mice. When fetal mouse pups that had a syndrome similar to Down’s were treated with nerve-protecting chemicals, some of the developmental delays that are part of the condition were removed.

Children with Down’s have an extra copy of chromosome 21, while mice engineered to have a similar condition are given an extra copy of a segment of chromosome 16. In both species, the development of certain motor and sensory abilities is delayed. These …