Anxiety during pregnancy can double a mother’s risk of having a hyperactive child, research suggests.
A study indicated that women who were very anxious in the last three months of pregnancy had children with more behavioural problems.
Those who had boys were twice as likely to have a child who showed problems with hyperactivity and inattention by the age of four.
The association between anxiety and behavioural problems in girls was also increased.
Lead researcher Professor Vivette Glover, of Imperial College, London, told the BBC the link only applied to women who had extreme anxiety, and reported feeling frequently "panicky" or "scared".
And she said the research should not make mothers even more anxious.
"Antenatal anxiety leads to the risk of hyperactivity increasing from one in 20 to one in 10.
"So nine out of 10 of the children even of the most anxious mothers are still perfectly OK.
"It is also important to note that mood swings are common in pregnancy and that most mums-to-be will have times when they are worried."
Professor Glover said children’s behaviour was usually attributed to either genes or parenting.
But she said this research suggested there was a chemical element as well.
"If the mother is very anxious this changes her chemistry, her hormonal levels.
"We know some of these hormones, for example cortisol, can cross the placenta and it may well affect the development of the baby’s brain in the womb."
Professor Glover said she wanted to do more research into how women could best tackle any anxiety they may have.
But for now, she said, every pregnant woman should take time to rest and relax.
"If you’re feeling very anxious, take time out," she said.
"Especially talk to people - talk to a friend, talk to your GP, try and do something that you feel relaxes yourself, sit with your feet up, listen to music."
The findings came from a survey of more than 7,000 mothers-to-be.
Each woman surveyed completed questionnaires designed to measure her level of anxiety at 18 and 32 weeks of pregnancy.
Women were identified as anxious if they scored in the top 15% of respondents.
Their children were assessed for behavioural and emotional problems just before their fourth birthday.
Researchers focused in particular on women who were anxious during their pregnancy, but whose levels of anxiety fell after delivery.
This was to see how the baby’s behaviour was affected by antenatal anxiety rather than their mother’s mood during their early years.
The research was co-ordinated by Tommy’s, the baby charity. It is released on the eve of National Pregnancy Week.
August 31, 2001