Previous studies have suggested that high anxiety levels during the later stages of pregnancy increase the risk of complications - and the need for a Caesarean.

It was thought that this might go some way to explaining why the rate of Caesareans has increased so sharply in recent years.

This finding that stress does not play a role in increasing the chance of a Caesarean section will be enormously reassuring to women

Maggie Blott

However, researchers in Sheffield say their new work indicates there is no such link.

The research team, led by Professor Pauline Slade of Sheffield University's Clinical Psychology Unit, studied 443 women in the third trimester of pregnancy.

They found that the likelihood of an emergency Caesarean was linked to factors such as previous history of undergoing the procedure, age, and medical risk.

But there was no link with anxiety about childbirth.

Contrary findings

The results ran contrary to a similar study conducted in Sweden which did find that anxious women were more at risk of an emergency Caesarean.

This was despite the fact that the Sheffield researchers recorded higher levels of anxiety among first time mothers than their Swedish counterparts.

Professor Slade said closer examination of the Swedish system may provide clues on how to reduce anxiety among expectant women in the UK.

Ms Maggie Blott, of the Royal College of Gynaecologists and Obstetricians, told BBC News Online, that the finding was good news.

She said previous research had indicated that women who received emotional support during labour, either from their partner or somebody else, were less likely to require an intervention such as a Caesarean.

It was plausible, she said, that the release of stress hormones - such as adrenalin, noradrenalin and cortisol - might in some way inhibit the process of labour.

However, she said: "This finding that stress does not play a role in increasing the chance of a Caesarean section will be enormously reassuring to women."

The vast majority of Caesareans are not planned.

The research is published in the British Journal of Obstetrics and Gynaecology.