Women who smoke or are overweight can seriously hinder their chances of having an baby by IVF, according to research published today.

Dutch scientists have found that smoking adds the equivalent of 10 years to the reproductive age of a 20-year-old woman whose fertility is poor.

Being excessively overweight reduces the chances of giving birth after IVF treatment, according to the research, published today in the journal Human Reproduction.

Doctors examined the success rate of the first cycle of IVF treatment in more than 8,000 women and found unexplained low fertility problems in 1,828 cases. The live birth rate for non-smokers in this group was 20%, but smokers had a live birth rate of 13%.

Smoking is acknowledged as being detrimental to unborn children, but it was not widely known that smoking could affect fertility levels in women.

Women who smoked were also much more likely to have miscarriages. About 21% lost their babies, compared with 16% of non-smokers.

The study found that overweight women reduced their chances of a live birth after their first IVF treatment by a third.

As with smoking, the harmful effect of being overweight was most pronounced for women with unexplained low fertility. Only 14% had a live baby, compared with more than 18% of normal weight women.

Professor Didi Braat, of Radboud University Nijmegen medical centre, one of the study's authors, said: "What our research clearly shows is that both smoking and being overweight unfavourably affect the live birth rate after IVF. Smoking has a devastating impact."

Professor Alison Murdoch, chairwoman of the British Fertility Society and head of reproductive medicine at the Newcastle Centre for Life, said: "There is evidence that people who smoke do have impaired conception, and they should be advised to quit smoking. Unfortunately we don't know precisely what the scientific basis of the relationship between smoking and fertility is."

"Women who are pregnant who smoke have impaired babies and poor outcomes," she added.