For 60 years, women have had the power to prevent unplanned pregnancy - and the responsibility for contraception was firmly placed on them.
From the pill to the coil to the implant and modern fertility apps such as Natural Cycles, dozens of contraceptives have been developed for women, while for men the options have remained limited and rather old-fashioned: condoms or vasectomies.
The promise of a contraceptive pill for men has been discussed for decades, with academics offering hope it was on the horizon - but nothing emerged.
Is all that about to change? A string of recent successful trials suggest the male pill is closer than ever before. Experts believe the conditions are right for a shake-up in family planning.
As conversation has grown around the side effects women suffer from the female pill - and with one in five pregnancies in the UK unplanned - demand for a new form of contraception is growing.
In November, it was announced that researchers at Dundee University have been given a US$900,000 ($1.4m) grant from the Bill & Melinda Gates Foundation to work on a contraceptive pill for men.
They are investigating ways to stop sperm reaching an egg during intercourse - a challenge that the professor leading the project compared to stopping Usain Bolt from reaching the 100m line. The team has been studying the behaviour of sperm in infertile men to aid their research.
Meanwhile, a team at the University of Edinburgh is testing a contraceptive gel for men, which combines testosterone and progesterone to switch off sperm production.
A volunteer taking part in the trial, James Owers, told the BBC he had been using the gel since February and had noticed no side effects so far, apart from "an increased sex drive".
In the US, scientists at the LA BioMed and University of Washington are working on a once-a-day tablet called 11-beta-MNTDC, which also reduces sperm production using a combination of hormonal actions, thus temporarily making a man infertile while having no effect on libido.
Trials on 30 men, who took the pills for one month, proved them to be safe to use and found male hormones fell daily, suggesting they work. Now, further research is needed to prove its effectiveness.
"These studies are the furthest we've got in developing an oral method. We know, conceptually, that it works in terms of stopping sperm production," says Dr Stephanie Page, co-leader of the trials.
If the next three-month trial is successful, it will progress to a six-month trial and then another, assessing its success as a contraceptive on 100 couples across the world, over a year. Page, however, estimates that it will take 10 years before it is available on the market.
What about side effects?
It seems a long time to wait - particularly considering the first prototype male pill was developed in 1974 and the female version has been around since 1960.
Much of the delay has come from the sheer complexity of the task: while women ovulate one or two eggs a month, men produce millions of sperm a day. "It's been a biological challenge," admits Page. "There are 100 million sperm when men ejaculate - do we have to get rid of all of them, or is it OK to have some stragglers?"
Side effects have been another issue. One trial for a contraceptive injection was halted in 2016 after 20 participants dropped out, due to side effects ranging from depression and acne to pain. (Such a courtesy was not afforded to women when the first female pill was trialled back in the 50s - one review found women who complained of nausea, dizziness, headaches and blood clots were discounted as "unreliable historians".)
"Any time you change someone's hormones, there will be side effects, and no drug is free of them," says Page. "Women currently bear the contraceptive burden and many tolerate side effects well, so hopefully that will be the case with men, too."
Sexism in the industry
There have been questions, too, over demand for a male pill - whether men would take it, and whether women would trust their partners to remember to, given that the physical and psychological costs of an unwanted pregnancy are so much higher for women.
Today's generation of young people seem keen for men to be more involved in family planning. A YouGov poll in January showed that a third of British men would be willing to take a pill, and in a global survey of 9000 men in 2012, 55 per cent said they would be willing to try a new form of hormonal contraception.
However, delays have also come down to sexism within the pharmaceutical industry and a lack of funding due to outdated views about who should take the responsibility for contraception, says Prof John Guillebaud, an expert in reproductive health at University College London.
"Especially since the economic downturn in 2008, potential investors have become reluctant to support research into contraceptives, particularly male," says Guillebaud. "They see that it is a woman's job to have babies or stop babies: because they have the babies, it is their responsibility."
Without investment in research and development, experts predict a long wait before a male pill becomes commercially available.
What men want
It is not deterring scientists in their endeavours. One team is working on a one-off reversible injection, another is testing a pill that can be taken shortly before sex to cause immediate temporary infertility. Page's team is working on a gel that suppresses sperm count to very low levels, which has had impressive results so far.
Dr Christina Wang, co-lead of that project, explains that a six-month trial with men in the US and the UK is already under way. "Men apply the gel to their shoulders and upper arms every day," she explains.
"It's absorbed and hormones are then steadily released into the skin. It probably has fewer side effects than other options, as it doesn't require as high a dose of hormones."
Michael Sworen, 30, has been trialling the gel in the US. "The gel irritated my skin for the first week," he says. "My libido is higher overall, and sex lasts longer than before. If this was a product on the market right now, I would happily use it if the price was comparable to other forms of birth control."
The gel is expected to be available in around five years, but researchers are still working hard on the male pill, as the majority of men who have expressed an interest prefer the idea of taking it orally.
"Men say it's what they want - or at least what they think they want," says Page. "We're constantly asked who will use male contraception, and until we have something out there, it's hard to measure."
Such news will be welcomed by millions of couples across the world who want to finally be able to share the contraceptive burden.
The Telegraph, London