Dr. David Greening from Sydney IVF says a study they have conducted suggests that for men with fertility problems, daily ejaculation for a week reduced the amount of DNA damage in sperm samples.

At the European Society for Human Reproduction and Embryology in Amsterdam the Australian fertility specialist said in general advice for couples had been to have sex every two or three days but Dr. Greening an obstetrician and endrocrinologist says men seeking to become a father should have sex each day, or ejaculate daily, for a week before their partner ovulates in order to maximise sperm quality.

For the study 118 men whose sperm had a higher-than-normal level of DNA damage were recruited - before the test, on average 34% of the group's sperm was rated as damaged, meaning that it was classified as "poor" in quality - ranging on an individual basis from 15 to 98%.

The men were not given any drugs or told to make any changes to lifestyle but were asked to ejaculate daily for seven days, after which their sperm was examined again and it was found that the damage to the sperm fell on average to 26% placing it in the category of "fair" in quality.

However while fourth-fifths of the men saw an increase in sperm quality, and many of them moved into the "good" range and out of the "poor" or "fair" categories, one-fifth saw a decline in sperm quality.

Dr. Greening says the improvements were "substantial and statistically highly significant" and that daily ejaculation not only boosted sperm quality for most of the men, it also helped sperm motility, another big factor in successful fertilisation - even though the volume of semen declined.

Though the research did not examine whether the improvement in sperm quality led to better pregnancy rates, previous research has shown that sperm that is less damaged and more mobile has a better chance of leading to a healthy baby.

Dr. Greening says the results may mean that men play a greater role in fertility than previously suspected, and that ejaculatory frequency is important for improving sperm quality - he suspects that the longer sperm stays in the testicular ducts, the greater its exposure to rogue oxygen molecules that damage cells and his advice to couples would be to have sex, or to ejaculate, daily in the run up to ovulation or to sperm donation for in-vitro fertilisation (IVF).

He says the optimal number of days of ejaculation might be more or less seven days, but a week seems manageable and favourable and that couples with relatively normal semen parameters should have sex daily for up to a week before ovulation date.

Dr. Greening says more research is needed to examine whether daily sex for men without fertility problems has the same benefits but he warns that having daily sex for too long - say a fortnight - would probably cut sperm numbers too much.

He recommends "lots of sex daily" around the time the woman is ovulating and says we are designed to breed in our youth and as men age they may not have as much sex as they did when they were younger, adding to the problem of infertility.

The findings could have implications for couples undergoing IVF as men are commonly told to abstain from sex for a couple of days to try and boost sperm numbers.

However fertility experts warn that it would be wrong to apply the results to all men as in some cases in men with low sperm counts, daily ejaculations may well reduce the sperm count still further and whilst sperm may be more healthy the reduced numbers could impede the chance of natural conception.