Smoking has a devastating impact on a woman's chances of conceiving with fertility treatment, research has found.

Women in their 20s and 30s who have problems getting pregnant are adding 10 years to their reproductive age if they smoke.

Even if they do conceive, women who use tobacco are more likely to suffer a miscarriage, according to the study in Human Reproduction.

Dutch researchers studied success rates of in-vitro fertilisation (IVF) procedures in more than 8,000 women, whose average age was 32.

The women were all starting their first cycle of IVF treatment and, while some had been diagnosed with a specific problem, many had "unexplained subfertility", meaning they had trouble conceiving but doctors could not pinpoint why.

Forty three percent of the women in the study were smokers who continued with the habit through their fertility treatment. The researchers found that the overall live birth rate for all the women was 15.2 per cent, and was highest for the women with unexplained subfertility, at 17.8 percent. But the birth rate among women who smoked was 28 percent lower than the overall average.

The impact of tobacco use on successful IVF treatment was most apparent among women who had unexplained fertility problems, with only 13 percent of the smokers having a live birth, compared with 20 percent of the non-smokers. Women who smoked were also much more likely to have miscarriages.

About 21 percent lost their babies, compared with 16 percent of non-smokers.

Professor Didi Braat, one of the study authors, from Radboud University Nijmegen Medical Centre, said: "Smoking has a devastating impact. It is comparable to adding a decade to the reproductive age of a 20-year-old.

Being excessively overweight also seriously hindered the chances of having an IVF baby, although women who were slightly fatter than normal were more likely to be successful. The birth rate also fell by 2 per cent for every year in age of the women involved in the study.

The researchers said that women undergoing fertility treatment could massively improve their chances of having a baby if they did not smoke and were of normal weight.

More than a third of British women in their 20s smoke, and the rate has only decreased slightly in the past five years.

One in seven couples experience problems in conceiving, and, in 20 percent of cases involving female infertility, no specific cause can be found.

Professor Alison Murdoch, the chairwoman of the British Fertility Society and the head of reproductive medicine at the Newcastle Centre for Life, said: "There is evidence people who smoke have impaired conception, and they should be advised to quit smoking.

"Unfortunately, we don't know precisely the scientific basis of the relationship between smoking and fertility."

(China Daily/Agencies April 8, 2005)