The study suggests that it is crucial that pregnant women receive extra support through stressful events © RexResearchers found that major upheaval dramatically raised the odds of a baby suffering ill health by the age of four.
It was particularly strong link if the mother-to-be suffered two traumatic experiences during the time she was expecting.
The study suggests that it is crucial that pregnant women receive extra support through stressful events.
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Researchers at the Institute of Psychiatry at King's College London interviewed more than 150 mothers before and after they gave birth.
They were asked about any stressful events affecting them, such as a family bereavement, separation, sudden unemployment and a difficult pregnancy.
Four years later, the women were interviewed about their children's health, including any illnesses that had led to them visiting their doctor or needing hospital treatment.
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The answers revealed a clear link with stress in pregnancy and ill health, with trauma early in pregnancy particularly likely to be linked to asthma or infections, the British Association for Psychopharmacology's annual conference heard.
Problems in the mother's life after the birth had little impact.
Possible reasons include changes in the mother's hormones or immune system affecting the development of the child's immune defences.
Jasmin Wertz, the researcher, told the Daily Mail that the result "suggests the stress experienced during pregnancy induces biological changes in the unborn child that render it susceptible to the development of illness later in life".
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Her supervisor, the psychiatrist Carmine Pariante, said: "We often talk about the concept of the foundation years, about the first two years of life being really important.
"This is true, but it is crucial that the foundation years start at minus six months."
With the study also showing high levels of depression among the stressed-out mothers-to-be, Dr Pariante said it is important that pregnant women get the support they need.
Dr Pariante said: "Everybody expects you to be happy because you are pregnant – it's very, very difficult to go and say you are depressed.
"But a pregnant woman who is depressed actually attracts a lot of empathy and sympathy."
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