An intriguing link between a mother’s stress levels during pregnancy and the effect on the brain of her unborn baby is revealed in a new study of children born in Bristol, England.
The research suggests that a woman who suffers anxiety during mid pregnancy is more likely to have a child who shows mixed handedness – neither left nor right handed - and that is associated with a range of conditions such as autism, dyslexia and hyperactivity. .
The findings, published in the medical journal Early Human Development, are based on information collected by the Children of the 90s project based at the University of Bristol.
Professor Vivette Glover from Imperial College in London analysed data on 7,400 mothers and children.
Mothers were asked to report whether, at the age of three 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.
In the analysis, children who used either hand for two or more tasks were classified as mixed-handed – 21.3 per cent of the boys and 15.4 per cent of the girls.
The results were compared against standard tests of mother’s anxiety at three stages during and after pregnancy.
Previous research with animals had suggested that there is a link between prenatal stress and laterality – our natural preference for using one side of the body.
While handedness is often inherited, it is also believed that it may be affected by conditions in the womb – specifically by increased levels of hormones such as testosterone.
When the results were analysed, Professor Glover found that women who suffered anxiety in the 18th week of pregnancy were more likely to have a child who showed mixed handedness. There was no significant connection with anxiety later in pregnancy or with ante-natal depression.
Professor Glover reports: “These findings show that the connection between antenatal stress and anxiety and atypical laterality observed in animal studies also exists in humans.
“After controlling for other factors, elevated anxiety at 18 weeks gestation was associated with a 20 to 30 per cent increase in mixed handedness as assessed at the age of three and a half.
“Given that there was no effect of postnatal anxiety, the results support the hypothesis that the effect of maternal mood took place in the womb. The results support the growing evidence for the importance of foetal programming in humans.”
While most ambidextrous people won’t have any problem, statistically they are more likely to have one of the associated neuro-developmental conditions than conventionally left or right-handed people. These include autism, dyslexia, attention deficit / hyperactivity and schizophrenia
Professor Glover says: “We should reassure those who are mixed handed that they will probably not have any of these other problems. We are talking about risk factors not certainties.
“However it may mean that interventions to reduce maternal stress or anxiety in pregnancy may reduce the prevalence of both mixed handedness and other associated developmental disorders such as dyslexia.”