Pregnancy stress 'causes defects'

Emotional stress can affect the developing child

Severe emotional stress during pregnancy may cause abnormalities in unborn children, say researchers.

Previous studies have suggested maternal stress during pregnancy - such as job loss, separation, or bereavement - may lead to birth defects such as cleft lip and palate and spina bifida.

A team of Danish researchers lead by Dr Dorthe Hansen set out to test whether there was any substance to this theory.

We know that stress alters body physiology and hence no reason this is not transmitted to the foetus via the placenta

Professor Peter Hepper, Queen's University of Belfast

They assessed the national medical registers in Denmark from 1980 to 1992 to identify all women exposed to severe life events during pregnancy and up to 16 months previously.

Severe life events were defined as deaths or first hospital admission for cancer or heart attack among members of the close family.

These were selected on the grounds that they were likely to be highly stressful to everybody, irrespective of personality, social support or ability to cope.

The researchers compared 3,560 women who experienced such events, with 20,299 women had no such emotional upset during their pregnancy.

The frequency of malformations was twice as high among stressful pregnancies.

Women who experienced stressful events in two consecutive pregnancies were particularly at risk.

Child death

The researchers found that the event that most increased the chance of birth defects to the unborn child was the death of an older child during the first three months of pregnancy.

This risk was further increased if this death was unexpected.

The researchers speculate that stress might impact on the development of the unborn child by stimulating the release of the hormone cortisone.

This can lead to raised blood sugar levels, and a reduction of oxygen supply to the tissues - both of which may lead to birth defects.

It is also possible that stress encourages the mother to increase her alcohol intake and eat a less healthy diet.

Professor Peter Hepper, of the Fetal Behaviour Research Centre at Queen's University of Belfast, said he was not surprised by the findings.

'Growing evidence'

He told BBC News Online: "We know that stress alters body physiology and hence no reason this is not transmitted to the foetus via the placenta.

"It is probably only in cases of severe stress - and it probably doesn't come much more severe than that resulting from loss of a child - that these effects occur.

"The findings support the growing body of evidence that long term chronic stress has adverse consequences for the developing foetus and every attempt must be made to help mothers who find themselves in this situation."

Tony Britton, of the Association for Spina Bifida and Hydrocephalus, told BBC News Online that a lack of the vitamin folic acid - either through poor diet or digestive problems - could be a factor.

He said the research emphasised how important it was for pregnant women to take folic acid supplements before and during pregnancy.

The research was published in The Lancet medical journal.