Heavy smoking 'reduces egg implantation'
Successful pregnancy linked to not smoking
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Thursday, 09, Nov 2006 11:09
Heavy smoking may limit women's chances of becoming pregnant by directly affecting the uterus, a new study claims today.
According to fertility experts in Portugal and Spain, smoking reduces the chances of the embryo (fertilised egg) from implanting in the lining of the uterus.
This was found to be the case even when the eggs were donated from other women, suggesting that cigarette smoking negatively affects the ability of the uterus to receive an egg independently of its effect on ovarian function.
Researchers studied both non-heavy smokers (under ten a day) and heavy smokers (over ten a day) receiving eggs through IVF treatment at the IVI-Valencia Foundation between the start of 2002 and June 2005.
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 (52.2 per cent), compared with just over a third (34.1 per cent) of the heavy smokers.
"This means we have confirmed previous data that shows light smoking has no significant impact on IVF cycles, either through affecting the ooctye or the uterus. But, heavy smokers have a much lower chance of achieving pregnancy."
But the researchers also found a paradoxical element in that embryos that were successfully implanted in heavy smoking women had a higher chance of becoming twins, with 60 per cent of the heavy smokers expecting twins compared to 31 per cent of the non-heavy smokers.
Explaining a potential explanation for this, Dr Soares said: "It could be that heavy smoking disrupts the stability of cells in the lining of the uterus differently in some women to others or triggers a response in the embryo itself, resulting in a reduced general pregnancy rate overall, but an increased chance of multiple pregnancy in those who do become pregnant."
Although he added that further research involving larger numbers of heavy smoking women is necessary, Dr Soares concluded: "We should now be telling patients, if they are heavy smokers, that even if fertilisation takes place they have less chance of achieving a successful pregnancy, whether they are trying to conceive naturally, or through IVF, and particularly with donated ooctyes."