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Stress causes small babies
Baby
Mother's state of mind may affect birth weight
Stress and anxiety during pregnancy could cause women to have smaller babies, scientists have discovered.

They believe the effect is caused by reduced blood flow through the arteries that feed the uterus.

Doctors from the Queen Charlotte's and Chelsea Hospital in London studied 100 expectant mothers.

They found pregnant women who were more anxious or stressed had "significantly abnormal patterns of blood flow through the uterine arteries".

The findings, published in the British Medical Journal, suggest that "the psychological state of the mother may affect foetal development and therefore birth weight".

The women were asked to rate their stress levels using a questionnaire.

The researchers carried out ultrasound scans to test the blood flow through arteries.

They found that those who were the most anxious during pregnancy had significantly abnormal blood flow patterns.

A "resistance index" measurement was taken of the extent to which the blood flow was impaired.

The researchers found that of the most anxious group, 27% had a resistance index high enough to be of "clinical concern". Only 4% in the less anxious group had similarly impaired uterine artery blood flow.

Vital differences

Stress
Stress has a major impact on the body
One of the study authors, Dr Vivette Glover, a reader in perinatal psychobiology, said the size differences recorded were small - around 10%.

But she said research had indicated that even small variations could have a potentially serious impact on health in later life.

Small babies are more likely to develop coronary heart disease, diabetes and depression in later life.

Dr Glover said more research was needed to determine why stress should impact on development.

"One possible reason is that stress raises the levels of hormones such as nor-adrenalin, which is known to constrict the blood vessels and decrease blood flow," she said.

"Another possible mechanism is that anxiety may have a chemical effect on the development of the blood vessels earlier on in pregnancy."

She added that it was not known when stress would have a worse effect on a foetus' development.

The study looked at foetuses in the late stages of development, but it could have more of an impact in the early stages when the placenta is being formed, said Dr Glover.

A previous study found the magnitude of the effect of stress on birth weight was similar to that found in children born to mothers who smoked.

Retarded development of the foetus has also been shown to be a risk factor for the potentially fatal condition pre-eclampsia.

The Royal College of Midwives welcomed the research and said it was "a key piece in the jigsaw" on birth weight.

But Ann Furedi, a spokeswoman for the British Pregnancy Advisory Service, said the study, although interesting, was probably of little practical value particularly as pregnancy was implicitly stressful.

"When a woman is pregnant often she will be very concerned about how the pregnancy is going to end," she said.

"Many pregnant women tend to worry about studies like this. My advice to them is to chill out - I suspect there is very little stress will do to effect the outcome of the pregnancy."

Ms Furedi said studies had shown that poverty was likely to have the most profound impact on the outcome of pregnancy.

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Dr Vivette Glover on stress and babies
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