Smoking slashes women's chances of IVF success
Life 7 April 2005
By Gaia Vince
Smoking has a "devastating impact" on a woman's chance of bearing a baby through IVF, new research shows.
Women undergoing IVF treatment are much less likely to succeed if they smoke, according to a large Dutch study. The effect of smoking on fertility was found to be so pronounced that it was equivalent of adding more than 10 years to a woman's reproductive age.
"Our study found that the effect of smoking more than one cigarette a day for a year reduced women's chances of having a live birth through IVF by 28% – that's the same percentage disadvantage that occurs between a 20-year-old woman and a 30-year-old woman," says Didi Braat, professor of gynaecology at the University Medical Centre in Nijmegen, where the study was carried out.
Braat and colleagues analysed medical data and questionnaire responses from nearly 8500 women aged 20 to 45, who had undergone IVF treatment at centres in The Netherlands between 1983 and 1995. More than 40% of the women were smokers and at least 7% were overweight – with a body mass index of 27kg/m2 or higher – at the time of their first IVF attempt.
The women's subfertility was attributed to one of four causes: fallopian tube problems, male partner subfertility, unexplained subfertility and other causes – mainly polycystic ovarian syndrome or endometriosis.
"Smoking had the greatest effect on those women with unexplained fertility problems, where IVF treatment led to 20.7% of non-smokers achieving a live birth, compared with just 13.4% of smokers," says Braat. "These results indicate that smoking may actually be causing the infertility problems these women were experiencing."
Toxic effects
It is not known exactly how smoking effects fertility, but Braat believes chemicals in the smoke may have a toxic effect on the endometrium – the lining of the uterus – or that it may produce a thickening and hardening of the zona pellicida, the fluid sac around the egg. The rate of miscarriage in the study was 21.4% among smokers and 16.4% for non-smokers.
The study also showed that being overweight reduced the women's chance of a successful live birth by as much as 30%.
"This study shows that, although women can't do anything about their age, they can improve their chances of becoming mothers by stopping smoking and not being overweight," Braat told New Scientist. "Other studies have shown that the negative effects of smoking on fertility are reversible, but we have no idea how long it takes after quitting smoking for fertility levels to resume non-smoker levels."
Journal reference: Human Reproduction (DOI:10.1093/humrep/deh898).
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