Smoking 'reduces chance of conceiving'
Scientists have produced hard evidence that smoking reduces the chances that a woman will conceive.
A new study shows that women who smoke, and are trying for a baby, take longer to conceive than non-smokers.
However, if they quit, their chances of becoming pregnant quickly improve.
The research was carried out by Dr Marcus Munafo, from the Imperial Cancer Research Fund's General Practice Research Group, based in Oxford.
It shows that on average, women who continued to smoke while attempting to conceive took two months longer to become pregnant than non-smokers.
However, women who quit smoking a year before attempting to conceive were likely to get pregnant within a similar time period as non-smokers.
Dr Munafo said: "The risks of smoking during pregnancy are well documented, including higher infant mortality, the increased risk of the baby developing serious respiratory infection, and lower birth weights.
"But many women may not be aware that by quitting, they are also greatly improving their chances of getting pregnant in the first place.
"The study clearly shows a link between smoking and fertility problems.
"When trying to conceive, many women often change their lifestyle by cutting down their alcohol intake, taking vitamins and minerals and eating a healthier diet.
"This study shows that stopping smoking should be a part of this pre-conception routine."
The study also found that there was no difference in the time taken to conceive between women who had never smoked, and women who had quit smoking at least a year previously.
Dr Munafo said: "This is good news for women smokers who are thinking of trying for a baby as it shows it is never too late to give up.
"A year after quitting, a woman's chances of conceiving return to that of a never-smoker.
"The message from this research is that if you want to get pregnant, you will not only improve your chances by quitting, you will also be doing something to protect the health of your child in the long term."
Mr Peter Bowen-Simpkins, of the Royal College of Obstetricians and Gynaecologists, said it was generally accepted that smoking affected fertility for both men and women.
The more people smoked, the greater the damage.
Mr Bowen-Simpkins said that the toxic chemicals contained in cigarettes damaged the action of the cilia - tiny hairlike structures - that lined the fallopian tubes and helped to transport the egg from the ovary to the womb.
In men, the same chemicals damage the ability of sperm to move around effectively.
There is also evidence to suggest that women who smoke are more likely to develop pelvic inflammatory disease, which also damages fertility.
Mr Bowen-Simpkins said: "If women want to get pregnant, they should stop smoking.
"At our IVF unit, we will not treat women unless they agree to stop smoking. The effect may only be minor, but when people are having problems trying to conceive it is worth trying anything that will improve their fertility."
The research is published in the Journal of Biosocial Science.