Heavy smoking may reduce female fertility by directly affecting the uterus making it less receptive and reducing the chances the embryo will implant, according to research published on line (Thursday 9 November) in Europe's leading reproductive medicine journal Human Reproduction.
The finding, from a team of fertility experts in Portugal and Spain, comes as a result of comparing the pregnancy rates between non-heavy smokers and heavy smokers, all of whom received donated oocytes.
Smoking has long been known to affect female fertility, but this study is believed to be the first to examine the impact of smoking in women who have received donated oocytes the situation that allows the most objective assessment of the role of the uterus in the outcome of IVF.
The researchers studied all the first cycles of oocyte-donated IVF treatments carried out at the IVI-Valencia Foundation between the start of 2002 and June 2005 741 in non-heavy smokers (under 10 cigarettes a day) and 44 in heavy smokers (over 10 a day). None of the women's partners were smokers and none of the oocyte donors were heavy smokers. The two groups of recipients were comparable and the number of embryos transferred in each cycle (between one and three) was also comparable between the groups.
Lead researcher Dr Srgio 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%), compared with just over a third (34.1%) of the heavy smokers.
"This means we have confirmed previous data that show 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. The fact that we see this result in a situation in which the oocytes were donated by other women demonstrates that cigarette smoking negatively affects the receptiveness of the uterus inde
Contact: Margaret Willson
European Society for Human Reproduction and Embryology