The lining of the womb may be damaged by heavy smoking, thereby reducing a woman's chance of getting pregnant according to recent research.
The study revealed that smoking can directly affect the uterus, making implantation in the wall of the uterus difficult.
The study was published in the journal Human Reproduction and it compared the pregnancy rates for IVF using donated eggs for those who either did not smoke or who smoked fewer than 10 cigarettes a day and for heavy smokers. Besides this none of the women's partners were smokers nor were there any heavy smokers among the egg donors.
Lead researcher Dr Sergio Soares, director of the IVI Clinic in Lisbon, said: 'The non-heavy smokers had a significantly higher pregnancy rate, with over half becoming pregnant, compared with just over a third of the heavy smokers. Heavy smokers have a much lower chance of achieving pregnancy.'
It was found that the risk of a multiple pregnancy was higher among heavy smokers who became pregnant, around 60 percent expecting twins compared to 31 per cent of the non-heavy smokers.
Further larger-scale studies were needed to establish the truth of these findings. While smoking has long been known to cause reduced fertility and low birth weight infants its effects on the uterus have been demonstrated only in this study.
Dr Soares concluded: 'In spite of all the noise generated about the effects of smoking in a series of health areas, its possible effect on uterine receptiveness has never been evaluated until now.
'Our study is just the first step on this path, and certainly not the last, but it means that we should now be telling patients, if they are heavy smokers, that even if fertilization takes place they have less chance of achieving a successful pregnancy.'