Male contraception has been limited to the same two options for more than a century: wearing condoms or having a vasectomy. It can hardly be called a choice, especially as vasectomies are generally a permanent procedure.
In comparison, when it comes to reversible forms of birth control, women are able to choose between a dozen methods ranging from the pill to hormonal injections, an implant, a patch, an intrauterine device (IUD), a diaphragm, a vaginal ring, female condoms or spermicide.
Granted, the scenario that contraception seeks to avoid is a woman getting pregnant, and it sounds mathematically easier to prevent an ovary from releasing an egg or two, or creating a barrier around them than to try to disable the millions of sperm trying to swim to them.
But as women increasingly speak out about the hassle of staying on top of their reproductive cycles, a significant proportion of men are showing interest in helping to relieve their female partner of the burden of birth control.
A 2018 YouGov poll found that 79 per cent of the 1,600 British men surveyed thought contraception should be a shared responsibility.
"Men are starting to be more vocal about wanting it. Women are getting more vocal about wanting men to want it. So people are starting to pay attention," said Heather Vahdat, executive director of Male Contraceptive Initiative, which helps fund research in this field.
So, what options might men have in the future?
Here’s a look at some of the most promising methods in the pipeline.
The shoulder gel
Now here’s a way in which men could literally shoulder more of the burden of birth control: by applying a testosterone gel daily on their upper arms and back.
The gel, called Nestorone, contains both testosterone and a progestin, a synthetic form of the female sex hormone progesterone. The progestin blocks natural testosterone production in the testes, reducing sperm production to low or nonexistent levels. The replacement testosterone aims to maintain normal sex drive and other hormone-driven functions.
The effectiveness of the gel is being evaluated around the world in Phase 2 clinical trials funded by the US National Institutes of Health that aim to enroll 400 couples in total and are expected to conclude next year.
Professor Richard Anderson from the University of Edinburgh - where 30 men have already completed the trial - says the results so far are very encouraging.
"It worked really surprisingly well. We haven’t had any pregnancies. The guy's sperm counts stayed really reliably suppressed," Anderson told Euronews Next.
Régine Sitruk-Ware, a distinguished scientist at the Population Council’s Centre for Biomedical Research leading the Nestorone study, said the shoulder gel appears to have a key advantage: reliability.
"When it's used daily, it remains on the surface of the skin and then delivers steadily," she explained. "And we see it at an effective dose for up to three days, which means that if there is one day off, and the person has forgotten to apply it, there’s a kind of forgiveness".
But hold your breath. The Population Council doesn’t expect it to reach the market for another five years.
That’s because clinical trials must not only demonstrate that the product works in preventing pregnancies, but also that it’s fully reversible, meaning that couples who’ve used it and subsequently want a child do manage to get pregnant.
The male pill
Researchers have also been working on a male birth control pill containing dimethandrolone undecanoate, or DMAU.
The molecule can alternatively be administered in long-lasting injections. It suppresses two hormones needed to create viable sperm: follicle-stimulating hormone (FSH) and luteinising hormone (LH).
The tricky part is that suppressing these causes testosterone levels to drop as well, which often comes with unwanted side effects, such as lowered libido, acne, and mood swings.
Such side effects may sound familiar to the millions of women who take a birth control pill, but they’ve gotten in the way of bringing male birth control to market.
A promising study commissioned by the World Health Organization (WHO) into a two-hormone injection designed to lower sperm count was halted after safety reviewers judged it had too many side effects, particularly mood changes.
Interestingly though, 75 per cent of the 320 men enrolled in the trial said they wanted to continue using the shot.
Researchers have since been working on ways to tinker with other hormones to trick the body into thinking that testosterone levels are adequate and limit side effects.
The reversible vasectomy: 'Set it and forget it'
As women become increasingly reticent to hormonal forms of birth control, those advocating research into new male contraceptives say non-hormonal methods could be a smart bet.
Enter so-called "vas-occlusive techniques" - or reversible vasectomy.
It works by implanting a gel into the vas deferens (the duct inside the penis through which sperm leaves the body) that allows fluid to flow but stops sperm from travelling. It’s being developed as a one-time outpatient procedure that can last several years, either until the gel naturally starts dissolving or until the man decides to have it removed to allow his sperm to roam freely again.
For over four decades, scientists in India have been looking into a vas-occlusive synthetic gel called RISUG ("reversible inhibition of sperm under guidance") that's currently the only male contraceptive in Phase 3 clinical trials.
Studies have shown it to be effective, but only animal trials have so far fully demonstrated the product’s potential to be reversed. A water-based gel called ADAM developed by the company Contraline in the United States is also expected to start first-in-human trials this year.
"It’s not as daunting as it may seem," said Vahdat, whose non-profit organisation Male Contraceptive Initiative is helping fund the study into ADAM.
"It’s like a male IUD: a long-acting reversible contraceptive for men. You set it and forget it".
More trouble than it’s worth?
Whether they sound promising or unsettling, these new options are still years away from becoming a reality for men worldwide.
So why is it taking so long? "It really has been funding," said Vahdat.
Case in point: her non-profit, MCI, is the second-largest funder of research into male birth control after the National Institutes of Health, with just $1.5 million (€1.3 million) in grants each year - a drop in the ocean of drug research.
MCI and the Population Council say the pharmaceutical industry’s traditional risk-benefit model has caused companies to leave this field virtually untouched.
"If you think of taking a healthy patient, disabling a function (reproduction) and promising it can be restored, that’s more risky in terms of return than treating a disease," Vahdat explained.
From a regulatory perspective, it’s also somewhat of an ethical headache to give someone a medication with potential side effects if the end goal - preventing pregnancy - does not affect their body but their partner’s.
Those calling for more male birth control options say that way of thinking needs to be turned on its head.
"We propose a model of shared risk that is ethical because you are preventing the risk of pregnancy in a female partner, and we're considering the sum total of risk between male and female partner," Logan Nickels, research director at MCI, said.
While this idea has yet to win over health regulators and companies, it may be catching on more quickly among the general population.
In France, a new male birth control product has been making headlines in recent months: a thermal ring called Andro-Switch designed to bring the testes closer to the body to naturally raise their temperature.
The pitch: if worn at least 15 hours a day for a few months, it lowers sperm production enough to cause temporary and reversible infertility.
"I think that a lot of people are understanding that instead of a fifth hormone-releasing IUD on the market, maybe we can have one male contraceptive," Nickels said.
Recent studies suggest many men would consider hormonal birth control if it were available.
In the US alone, 77 per cent of sexually active men aged 18 to 44 surveyed in 2017 were "very or somewhat" interested in trying out a male form of birth control other than condoms or vasectomy.
"A few decades ago, people were simply grateful there were contraceptive methods. Now people realise it’s also a burden, and it’s more about sharing responsibility," Anderson, of the University of Edinburgh’s Centre for Reproductive Health, said.
"A number of men do want to step up to the mark".