A report from the University of Toronto also found that an epidural was more effective and had less impact on the newborn child than giving the mother narcotic injections.

The Toronto research was based on a review of studies involving more than 2,300 patients.

Some studies have detected an increase in Caesarean delivery after an epidural compared to other forms of pain relief.

But the review, published in this week's Journal of the American Medical Association, found no statistically significant increase in such deliveries following epidurals.

Narcotic injections "are the most frequently prescribed alternative pain relief to an epidural".

However, the researchers found that in routinely used doses, they have little effect on labour pain.

The researchers warned that if women suffer severe, unrelieved pain during labour they are at greater risk of developing depression and post-traumatic stress disorder.

They found that children born to mothers who received epidurals were more alert, had a lower incidence of mild acidosis, a disturbance of the body's acid-base balance that can cause breathing problems and diarrhoea.

Reduced stigma

Dr Stephen Halpern, co-author of the report, hoped the findings would put to rest some concerns about the use of epidurals - and the stigma some women feel in asking for them.

He said: "Basically, if a woman needs pain relief, she should feel free to ask for it."

Dr Halpern, director of obstetrical anesthesia at Women's College Hospital in Toronto and an associate professor at the University of Toronto, said the research found that epidurals are not the cause of C-sections. Rather, they are often used because complicated deliveries that end in C-sections are among the most painful.

The clinical trials, conducted in Europe, the United States and Canada, included a total of 2,369 patients.