Women undergoing IVF; treatment who smoke are much less likely to have a baby than non-smokers, Dutch researchers say. The study, carried out by a team based at the University Medical Centre in Nijmegen, showed that smoking more than one cigarette a day cuts the chances of success by 28 per cent - a difference equivalent to that between a 20 and a 30 year old woman undergoing treatment. The research, published in the journal Human Reproduction, also showed that being overweight lowers the chances of conceiving.
Although several previous studies have shown that smoking affects both male and female fertility, the latest findings add weight to the link, since the team investigated 8,457 women undergoing fertility treatment. Doctors at 12 centres in the Netherlands collected data from patients enrolled in the OMEGA study, which was started in 1995 to investigate the effects of hormone stimulation. The scientists looked at the success rate of the first cycle of treatment, information on reproduction and lifestyle, and medical records of IVF treatment from 1983-1995. More than 40 per cent of the women were smokers at the start of their treatment, and more than seven per cent were overweight.
The researchers found that overall, the live birth rate for smokers was 28 per cent lower than that of non-smokers. The harmful effects of smoking on success rate was strongest in women with unexplained fertility, who had a live birth rate 35 per cent lower than non-smoking women in this group. 'These results indicate that smoking may actually be causing the infertility problems these women were having', said study author Didi Braat. As well as affecting the chances of conceiving a baby, smoking also increased the chances of a miscarriage occurring, by almost 25 per cent. Being overweight also decreased the success rate of IVF treatment by a third, and as with smoking, the effect was greatest in women with no obvious reason for their infertility.
Braat said that the research 'clearly shows' that both smoking and being overweight 'unfavourably affect the live birth rate after IVF'. She added that smoking has a 'devastating impact', comparable to adding a decade to the reproductive age of a 20-year-old woman. Lead researcher Bea Lintsen said that the positive news from the study was that couples - particularly those with unexplained fertility - 'may be able to improve the success of IVF treatment by quitting smoking and losing weight'. Clare Brown, chief executive of the charity Infertility Network UK, said the research highlights the importance for couples who smoke, particularly the women, to stop. 'NICE guidelines on fertility treatment published in February 2004 also recommend that couples give up smoking as well as cut down on alcohol consumption before embarking on fertility treatment', she added.