Would-be fathers may not be "match fit" to get their partners pregnant, with one in six still smoking and almost 5% taking drugs such as cannabis and cocaine, according to a new poll.
The survey of 500 men and 500 women also found some women were disappointed in their partner's efforts to get healthy while trying for a baby.
Just 41% of men adopted a healthier diet compared to 59% of women, while 27% of women said they tried to reduce their stress levels compared to just 19% of men.
Overall, 15% of women thought their partner could have done more to improve their chances of conception.
Of these, 48% said their partner could have improved his diet, 44% said he should have exercised more and 37% believed their man drank too much.
Overall, 71% of men continued to drink while trying to get their partner pregnant, with 11% drinking more than the recommended 21 units of alcohol a week.
Research has suggested that heavy alcohol consumption can affect the quality of a man's sperm, alongside other damaging factors such as smoking.
Dr Allan Pacey, senior lecturer at the University of Sheffield School of Medicine and Biomedical Sciences, said: "It's clear from the survey results that some men really aren't match fit to start a family and they could do more to increase their chances of becoming a dad.
"Women are much more in tune to fertility issues than their partners and we need to do more to educate men about those simple steps they could take to cut out those things which we know harm male fertility."