LONDON (Reuters) - Smoking reduces the chances that women undergoing IVF fertility treatment will have a baby -- equivalent to aging them ten years.
Being overweight can also limit the odds of becoming a mother, according to new research reported on Thursday.
"What our research clearly shows is that both smoking and being overweight unfavorably affect the live birth rate after IVF," said Professor Didi Braat of Radboud University Nijmegen Medical Center in the Netherlands.
"It is comparable to adding a decade to the reproductive age of a 20-year-old. This means it makes her the equivalent of a 30-year-old non-smoker in reproductive terms."
In the study, which is reported in the journal Human Reproduction, the researchers examined the success rates of 8,457 women after their first cycle of IVF (in-vitro fertilisation) and life-style factors.
Women who were overweight had a 33 percent lower chance of having a child after the first treatment than other patients in the study.
The effect of smoking and being overweight were most prominent in women with "unexplained sub-fertility," where the reason they do not conceive naturally is not established.
That suggests that these women in particular would be able to improve their chances of having a child if they quit smoking and lost weight, researchers said.
The live birth rate of smokers with unexplained sub-fertility was 13 percent. In non-smoking women with the same diagnosis it was 20 percent, said Dr Bea Lintsen, a co-author of the study.