IVF success compromised by heavy smoking

Nov 13 2006

Fertility experts say the women who are heavy smokers are less likely to become pregnant through IVF treatment, even when donated eggs are used.

Researchers at a fertility clinic in Lisbon, Portugal, say they found that smoking more than 10 cigarettes a day makes the womb less receptive to the embryo and reduces the odds that it will implant and result in a pregnancy.

Smoking has been known for some time to affect a woman's fertility but lead researcher Dr Sergio Soares and his team believe their findings are the first to show heavy smoking has an independent impact on the uterus.

Dr. Soares says cigarette smoking negatively affects pregnancy probability even when the eggs come from a non-smoker, and even if fertilisation takes place, heavy smokers have less chance of achieving a successful pregnancy.

The scientists from Portugal and Spain compared the success rates of in-vitro fertilisation (IVF) treatments using donated eggs on 44 heavy smokers who puffed more than 10 cigarettes a day, and 785 women who did not smoke or were light smokers; all the women were married to non-smokers.

Soares says the non-heavy smokers had a significantly higher pregnancy rate, with over half becoming pregnant (52.2 percent), compared with just over a third (34.1 percent) of the heavy smokers.

He adds that light smoking did not appear to have any impact on the receptiveness of the uterus to the embryo.

In what is in many ways a paradox, although heavy smokers were less likely to get pregnant, they had a higher multiple pregnancy rate; sixty percent of the heavy smokers had multiple births compared to 31 percent in the other group.

Soares says larger studies are needed to determine if components in tobacco affect the womb differently in various women, possibly impairing implantation in some women and having the reverse effect in others.

Apart from impairing fertility, smoking has also been shown to increase the risk of heart attack and stroke, respiratory problems and lung and other cancers.

Dr Soares said heavy smokers should be told that even if fertilisation takes place, they have less chance of achieving a successful pregnancy but are more at risk for multiple births which are less safe for mothers or babies.