Monday, September 20, 2004

Stress In Pregnancy Puts Babies At Risk

By Jo Revill
Health Editor, The Observer UK

An intriguing link between levels of anxiety in pregnant women and the damaging effect on the brain of the unborn child will be shown this week in 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 found such a link, and they believe it may be necessary for midwives to tackle mothers' stress levels to reduce the effects on the foetus.

The findings are based on information collected by a project based at 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 either hands 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 can use 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 of three-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 as mixed handed - something they found in 21 per cent of boys and 15 per cent of girls.

After allowing for other factors, Glover found that a heightened level of anxiety at 18 weeks of pregnancy was associated with a 20-30 per cent rise in mixed handedness.

In a study she will present to a conference in Bristol this week, she said: 'Given that there was no effect on postnatal anxiety, the results support the hypothesis that the effect of maternal mood took place in the womb. The results support growing evidence for the importance of foetal programming in humans.'

Previous research in animals has suggested that there might be a link between antenatal stress and laterality - our natural preference for using one side of the body. Until now there has been no research to show if the same effect applies in humans.

One interesting component of the study, published in the journal Early Human Development, is that handedness was only affected by the anxiety in the middle of the pregnancy. No significant effect was seen in mothers who were anxious at 32 weeks, or eight weeks after the birth of the child. Whether the mother was depressed or not made no difference: it was the mother's mood and a feeling of being worried or stressed that counted.

Unlike our closest genetic relative, the chimpanzee, humans tend to heavily favour one hand or the other. Some scientists believe this has been crucial to the evolution of man, because the division between the right and left-hand side of the brain, which governs the handedness, affects the way our brain develops.

The Children Of The 90s study is a continuing project based in Bristol, which enrolled 14,000 mothers during pregnancy in 1991 and 1992, and has followed the lives of both children and parents in minute detail ever since. An earlier study from the project showed that antenatal anxiety in late pregnancy increased the likelihood of the child exhibiting behavioural or emotional problems at both four and seven years.

The new findings do not mean that ambidextrous people will definitely develop the problems such as autism or dyslexia, but they will statistically have more chance of having one of the conditions.

'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,' said Glover.

'However, it may mean that interventions to reduce maternal stress or anxiety in pregnancy may reduce the incidence of both mixed handedness and other associated developmental disorders such as dyslexia.'

Guardian Unlimited © Guardian Newspapers Limited 2004

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