Jo Revill for the The Observer

An intriguing link between levels of anxiety in pregnant women andthe damaging effect on the brain of the unborn child will be shown this weekin a new study of ambidextrous children.

Researchers have discovered that women who are very anxious in the middle of their pregnancies are significantly more likely to have a child who is ambidextrous or 'mixed handed', a condition associated with autism, dyslexia and hyperactivity. It is the first time scientists have foundsuch a link, and they believe it may be necessary for midwives to tacklemothers' stress levels to reduce the effects on the foetus.

The findings are based on information collected by a project basedat the University of Bristol which looked at the lives of more than 7,400 mothers and children.

The data was analysed by Professor Vivette Glover from Imperial College, London, who examined the rates of mixed handedness or atypical laterality as it is known. The condition - where people can use eitherhands for a range of tasks - is often inherited, but is also thought to be affected by the hormonal levels in the womb, particularly by the rates of testosterone.

Scientists make a distinction between ambidextrous people who canuse hands completely interchangeably and those who are mixed handed, who have a favoured hand for each task, although it may not be the same one.

Mothers were asked to report whether, at the age ofthree-and-a-half, their child used the right or left hand for six tasks - drawing, throwing a ball, colouring, holding a toothbrush, using a knife and hitting things. Children who used either hand for two or more tasks were classified asmixed handed - something they found in 21 per cent of boys and 15 per cent of girls.