Some men should have sex every day to maximise the chances of getting their partner pregnant, researchers say.

It is known for couples with fertility problems to abstain from sex for several days to boost sperm numbers before trying to conceive.

However, the Sydney University team, addressing the American Society for Reproductive Medicine conference, said this could mean poorer quality sperm.

One UK expert said daily sex might be better for men with damaged sperm.

The Australian scientists studied 42 men whose sperm had been found to be an abnormal shape when examined under the microscope.

They were told to ejaculate daily for seven days, and these samples were compared with those taken from them after three days' abstinence.

All but five of the men had less sperm damage in their daily samples compared with the post-abstention sample.

Fertility myth

Dr Allan Pacey, the secretary of the British Fertility Society, said that while not having sex allowed the numbers of sperm to build up, there was a "trade-off" between quality and quantity.

"This research shows that when you put people on a daily ejaculation regime, it reduces the figure for DNA damage.

"If you can go from 30% to 20% that is quite a big shift and that should have some implications for fertility.

"There are men out there who think, or whose partners think, that limiting ejaculation will make them more fertile.

"I remember one couple in which the woman would only let the man ejaculate when she was in her fertile period, so the poor chap was going without for almost a month at a time."

He said that if a couple was initially trying to get pregnant, an interval of two to three days was probably advisable - whereas a man with high DNA damage and a "decent" sperm count should try more often.