The EUROPOP survey of 16,000 women in 17 European countries shows that a woman is 100% more likely to go into premature labour if she is of low socio-economic status, left school at 16, is a teenager, lives alone or is single.

Other significant risk factors include:

• Working more than 40 hours a week
• Doing a physically strenuous or stressful job or one which involves standing for long periods
• Commuting long distances to work
• Being unemployed
• Being under 20 or over 34 years old
• Smoking during pregnancy
• Being overweight or underweight.

The survey looked at women who gave birth between 1995 and 1997 and classified them according to whether they had a normal, moderately premature or severely premature birth.

It is published on Monday at a conference on the problems of prematurity.

Premature birth is one of the major risk factors for neonatal babies.

The conference is part of National Pregnancy Week which begins on Sunday.

Socio-demographic factors

The study's author, Professor Gian Carlo Di Renzo, says it represents the most conclusive proof yet of the link between socio-economic factors and premature birth.

A mother's stressful job can harm a foetus

He said: "For years, the recognised risk factors for prematurity have been those linked to a woman's previous obstetric history and to medical complications in pregnancy.

"This is still the case, but what this study shows clearly is that premature birth is also inextricably linked to socio-demographic factors such as class, education and the type of job you do."

The UK has one of the highest rates of premature births and teenage pregnancies in Europe.

Around 100 babies a day are born prematurely in the UK.

The survey also shows that the UK is one of the only European countries studied which does not give special leave to women who have health problems linked to their pregnancy.