Couples trying to conceive are urged to think about their lifestyle choices
Couples trying to conceive through IVF could be significantly harming their chances if they share the equivalent of a bottle of wine a week, experts warn.
If both partners drink six units a week - equivalent to half a bottle of wine each - their chance of a live birth is cut by a quarter, a study suggests.
Doctors said couples may want to "play it safe" and not drink at all to maximise their chances of IVF success.
The findings are based on a US study of more than 2,500 couples.
The study was presented at a fertility conference in Atlanta.
In the study, men and women who each had six UK-equivalent units a week - the equivalent of two strong pints of beer or two large glasses of wine - or more "significantly reduced their likelihood of pregnancy".
For women, it cut their chances of getting pregnant by 18%, while men reduced their chances of a live birth by 14%.
Overall, half of the women and a third of the men drank less than one alcoholic drink a week, while 4% of women and 5% of men drank at least once a day.
Women who had between one and nine units of white wine a week were 24% less likely to have a live birth and had a 23% greater chance of failed implantation of the IVF embryo.
Men who drank a beer daily contributed to a 30% lower chance of a live birth and a 38% greater chance of failed implantation.
Dr Brooke Rossi, who led the study at the Harvard Medical School in Boston, told doctors at the American Society for Reproductive Medicine conference: "In general, women are told they should stop drinking when they are trying to achieve pregnancy."
Tony Rutherford, of the British Fertility Society, said: "This is further evidence to suggest that alcohol does have an impact and that those women who try for a baby should think about their lifestyle choices.
"Eggs and sperm take at least three months to develop so women have got to stop smoking, reduce alcohol consumption or, if you are overweight, correct that weight that far ahead if you want to maximise your chances of conception."
He said the couples in the study had fertility problems, so there might be other reasons why alcohol affects their chances of a live birth.
But he said: "It may be that if you are trying for a baby with IVF and want to maximise your chances of success, you may want to 'play safe' and not drink at all."
Professor Ian Gilmore, president of the Royal College of Physicians and chairman of the Alcohol Health Alliance, said the advice to abstain applied to both partners in a couple if they were having difficulty conceiving.