Image caption Condoms are the only real reversible contraceptive choice for men currently

While women can choose from over 10 methods of reversible contraception, men have few options: namely the condom, or the more extreme and often irreversible option of vasectomy.

This is despite decades of research, dozens of medical trials, and a range of methods that have been shown to work.

So what is holding back a reversible male contraceptive?

The contraceptive pill was approved for contraceptive use 50 years ago, and in the following years, lent momentum to the women's movement.

But now that women have been taking patches, pills, jabs and implants for so long, many are questioning whether it should be the turn of men.

Professor Richard Anderson, Professor of Clinical Reproductive Science at Edinburgh University, told Health Check on BBC World Service: "Women are increasingly recognising that to start using contraception perhaps as a teenager, right through to you're 50, interspersed with a few pregnancies, is a pretty bad deal, and it's about time someone else stepped up to the mark."

Reversible contraceptive

News stories about male 'pills' regularly hit the headlines. "The perennial thing is that it's always five years away, and has been for a very long time", says Richard Anderson.

While women are fertile for a short period of each month, from puberty to menopause, men produce millions of sperm every day, and can theoretically father a child from puberty until death.

There is a need for a contraception that is long-term and reversible Professor Sujoy K Guha, Expert in male contraception

"The main problem is to get that sperm count to zero, or very nearly zero, all the time. And it has to be absolutely consistent, every day of the week," explains Richard Anderson.

But, decades of research have shown that men's sperm production can be stopped with hormones, just like a woman's fertility can be switched off by the pill or other hormonal contraceptives.

Furthermore, some imaginative non-hormonal methods have also been developed over the years.

Ultrasound has been shown to cause temporary male infertility, while Professor Sujoy K Guha, an Indian biomedic, invented RISUG (Reversible Inhibition of Sperm Under Guidance) - a polymer that can be used as a reversible vasectomy.

200 Indian men have undergone the procedure in advanced clinical trials. The vas deferens is injected with a small amount of the preparation. Early results indicate that it can last for 10 years, and is reversible by injecting the vas with sodium bicarbonate.

This Indian solution to a burgeoning population has attracted attention from men from industrialised nations.

"Every few weeks we get people coming from the West. A lot of them write to us, and a number of them even come and sit in our hospital, asking for the injection," says Guha.

"So there is a need for a contraception that is long-term and reversible."

But Guha's product might be too efficient to make economic sense, as a man may only have it done once or twice in his lifetime.

Who profits?

Elaine Lissner, Director of medical research programmes at the Parsemus Foundation and advocate for male contraception, explains: "This is a nightmare product for a pharmaceutical company. For a pharmaceutical company, the ideal method is expensive and short-acting. And for a man the ideal method is cheap and long-acting."

Furthermore, why focus your efforts on medication for young, healthy people, when the most profitable drugs markets are those in the rapidly ageing industrialised world?

Chemist Carl Djerassi, one of the female pill's inventors, explains: "The countries that really make money and sell their drugs - Western Europe, Japan, North America, which are the three major markets. They are getting older and older. They're interested in the diseases of an ageing population."

And while profit might be small, the potential for legal payouts linked to a contraceptive's use could be massive.

"There's no question that if the male pill were around right now that there would be millions of men who would take it, and some of them would then be approaching 55, 65, 70." And some may experience problems, like erectile dysfunction.

"They will blame it on the pill," he said.

Pharmaceutical company Bayer Schering Pharma, who make many of the female contraceptives on the market, conducted trials into a male contraceptive in 2004. Their product was an implant with quarterly injections, but development was halted.

In a statement they said that they were "not convinced that this inconvenient regimen (although efficient with a tolerable side effect profile) would find sufficient market acceptance."

"Compared with other pipeline assets, this project with non-ideal administration and questionable acceptance, could not be prioritised for going into Phase III despite a generally positive Phase II result."

So, without pharmaceutical backing, will male birth control ever reach the market?

Elaine Lissner says it may. "It's our governments and our non profit sector that are going to have to do this."

The World Health Organisation, governments, and major donors are now backing research into new male contraceptives - with the Bill and Melinda Gates Foundation recently donating a significant sum towards the ultrasound method.