When hormonal contraceptive pills hit the market in the 1960s, it revolutionized women’s control over their own bodies.
The pill gave women the freedom to choose when they want to start a family, but unintended pregnancies are still common. Nearly half of the pregnancies that occur every year are unintended, both in the U.S. and around the world. Could a contraceptive for men help?
We might find out in the next decade. Scientists are successfully experimenting with pills, gels, and implants that would allow men to share contraceptive responsibility with women. Many are more convenient and foolproof than condoms or easily reversed than vasectomies, and some are being developed without the hormones that typically cause bothersome side effects for women.
“I see it as a huge shift in equity, ” says Heather Vadhat, the executive director of the Male Contraceptive Initiative, an organization that funds contraceptive research. Understanding how these new birth control methods work requires a refresher on the male reproductive system.
Sex Ed 101
For men, successful reproduction begins with the right cocktail of hormones, notably testosterone. They signal the body to start producing sperm, a process called spermatogenesis. It takes about 74 days for sperm to develop and mature, a regeneration process that’s constantly taking place after a man reaches puberty. Mature sperm are stored in the testes, a reserve of reproductive material that’s regularly restocked.
When a man ejaculates, more than 250 million sperm leave the testicles and begin their hunt for an egg to fertilize. If they find themselves inside a vagina, the best swimmers propel themselves forward, through the vagina, past the cervix, and into the uterus where, if they stumble upon a healthy, fertile egg, they lead to conception.
While modern female birth control uses hormones to disrupt the process that produces one to two fertile eggs a month, male birth control must stop millions of sperm in their tracks.
Male hormonal birth control
Hormones are being used to stop the male reproductive process by specifically targeting spermatogenesis, slowly shutting down the sperm production process.
The most researched version of this is a topical gel applied to a man’s shoulders and arms every day. The gel contains a synthetic female hormone called progesterone that lowers testosterone, a male reproductive hormone, to a level where he can no longer produce sperm. As the gel is absorbed into the skin, small amounts remain just underneath, slowly releasing contraceptive hormones that make the man infertile for as long as he continues to use the gel.
“There are very few side effects directly related to the gel, and the results are really promising,” says Christina Wang, an expert on male contraception at the University of California, Los Angeles, who’s leading clinical trials on hormonal contraception in men.
To prevent side effects like low libido, the gel also contains a small amount of testosterone that’s added back into the body while still ensuring testosterone levels are too low to produce sperm.
One 2012 clinical trial tested the gel in 99 men and found that almost 90 percent of them experienced temporary infertility. Participants reported side effects similar to female hormonal birth control, such as weight gain, acne, low libido, and mood swings.
Hormonal gels are already used to treat hormone deficiencies, which is one reason the method is appealing to researchers: “We know men can use it,” says Wang.
Wang has recruited 400 couples to test a male birth control gel. She estimates that a contraceptive gel could be on the market and widely available to men by about 2030.
Vasectomies are another option for male birth control. They have been performed since the late 19th century, but became more popular during the 20th.
The procedure is named for small tubes in the scrotum called the vas deferens. When sperm leaves the testes, it travels down these tubes and mixes with semen. Vasectomies work by blocking this pathway in the vas deferens, preventing the sperm from leaving the body. Often doctors will surgically insert a special clip to block the tubes, or they might cut and tie the vas deferens tubes directly.
In the wake of the U.S. Supreme Court’s decision to overturn Roe v. Wade, which ensured women could access abortion care, doctors have seen an increase in men looking for vasectomies.
“One of the things we’re seeing is men thinking they can reverse vasectomies when they want,” says Vahdat. “But a vasectomy is pretty straightforward, and reversal is not.”
Depending on how the vasectomy is reversed, there’s anywhere from a 60 to 90 percent chance fertility can be regained, but the process requires surgery and success isn’t guaranteed.
There may be new options on the horizon. Vahdat is excited about a company called Contraline that injects a gel into the vas deferens. The gel is meant to block sperm, just like traditional vasectomies, but over time the gel liquifies and is absorbed into the body.
The gel is in early clinical trials in Australia, and the participating men will be evaluated for the next three years.
A pre-sex pill
After sperm are produced, tunneled through the vas deferens, and deposited in the vagina, they must still swim their hearts out to successfully cause a pregnancy.
But a study published earlier this year in Nature Communications shows promise for an “on-demand” contraceptive pill that could be taken about 30 minutes before intercourse and whose effects would wear off after about a day. The drug works by targeting an enzyme called Soluble adenylyl cyclase (sAC), essentially the “on switch” that tells sperm to start swimming. When that enzyme is suppressed, sperm can’t get any farther than the vagina.
“They’ll be immotile; they’ll just sit there and twitch,” says Lonny Levin, a pharmacologist at Weill Cornell and one of the study’s authors.
When an experimental drug was given to mice, they were infertile after 15 minutes. Two hours later, their fertility returned to normal.
“I said holy mackerel this is the holy grail. This is a male contraceptive,” Levin says.
After about an hour inside the vagina, the sperm die and pregnancy is averted.
Levin and his research partners hope to test these enzyme blockers on humans in the next two to three years and think it could still be a decade until those trials produce results that ready the pill for market.
Will men use them?
“There was a stereotype that men won’t use [birth control], and women won’t trust them,” says Vahdat.
But a survey shared at a World Health Organization webinar in September 2022 (seen in a recording here) suggests that’s not entirely true.
A global survey of 5,000 men who have sex with women showed many were interested in trying a contraceptive. The least enthusiastic participants were found in the U.S.—about 40 percent of men in the U.S. said they would try birth control in the next year. And the most excited were in Nigeria—nearly 80 percent of men said they were interested in taking a new form of male contraception.
Steve Kretschmer, executive director of consulting firm DesireLine, conducted the survey. He said countries where women’s contraceptives were already common had men who were slightly less interested in taking birth control. But overall, in all countries surveyed, men's interest increased over time.
His data also showed that a majority of women in each country said they would believe their male partner if he told them they were taking birth control.
Vahdat is eager for these new contraceptives, reproductive advancements that have been a long time coming. Among her peers, she says, there’s a running joke that birth control for men has been “a couple years away for 50 years.” But, she adds, it finally feels within reach.
When male birth control is widely available, Vahdat expects it to dramatically reframe how we think about reproduction and who’s responsible for it.
“We just don’t think of men as contraceptive beings. It’s so synonymous with female autonomy,” she says. “I feel confident it’s going to be game-changing.”