Damaged sperm is a problem for almost 60 per cent of Australian men visiting fertility clinics, but a short ''health boost'' can turn that around, research shows.
Data from a study to be issued today, the anniversary of the birth of the world's first IVF baby, Briton Louise Brown, has found men are now the primary cause of a couple's infertility.
Sydney specialists tested the semen quality of 800 men who attended one fertility clinic with their partners and found 58 per cent had severely ''fragmented'' sperm.
In these men, more than 20percent of the sperm DNA was so damaged it was unlikely to cause a pregnancy.
''That's an incredibly large proportion of men with a male factor problem that has a serious impact on the couple's chances of having a baby,'' medical director of Fertility First Anne Clark said.
''And it's a very long way from the beginnings of IVF 30 years ago when the focus was very much on a woman's reproductive problems.'' The good news was these men could significantly improve sperm quality in two months with basic lifestyle changes.
''More than 100 of these men agreed to stop smoking, cut back on caffeine and alcohol, take vitamin and mineral supplements and cut back their weight if that was a problem, and our results were impressive,'' she said.
The findings, to be presented at a Fertility Society of Australia meeting in October, showed damage levels dropped in 73 per cent of the men.
In more than 40 per cent of cases, the man's partner fell pregnant in the following three months, including 11 natural pregnancies.
None of the pregnancies miscarried, despite 30 per cent of the women being aged over 38.
''As far as we know this is the first quantifiable proof of just how much changing your lifestyle with a short health boost can improve male fertility,'' Dr Clark said.
Smoking and obesity have been found to have the biggest impacts on fertility for ageing couples.
When a man hits 40 the chance of his partner in her 30s conceiving either naturally or with in-vitro fertilisation is halved.
A 9kg weight increase doubles his chance of fertility problems again.
''The take home message is that infertility is very much a couple's problem, not a woman's problem,'' Dr Clark said.
''Louise Brown was born 30 years ago using a technology invented to deal with a female problem but these days it's very much about men.'' More than 80,000 IVF babies have been born in Australia. AAP