Every couple of months, starting in 2008, clinicians injected dozens of men across eight countries with a serum containing the hormones progestin and testosterone. The men then had unprotected sex with their female partners, as part of a male-birth-control trial orchestrated by Conrad, a Virginia-based nonprofit devoted to reproductive-health research. Three years into the trial, things appeared to be going well: just four women had gotten pregnant.
There was one big catch, however. While Conrad had anticipated that the hormones might have a few minor side effects—weight gain and acne among them—some of the men developed more-severe reactions, including depression and ramped-up libido. This spooked the panels that were overseeing the experiments, and in April 2011, Conrad shut down the study.
Though they’re used by almost everyone, contraceptives seem to have advanced less in 50 years than cellphones have in five. The problems with the current birth-control arsenal are well known: The pill is the most common female contraceptive method in the United States, but nearly a third of American users are so dissatisfied that they abandon it within the first year. That’s because the pill, like all hormonal forms of birth control, can have a number of negative side effects, including nausea and mood changes. Intrauterine devices and implants are by far the most-effective forms of reversible birth control, but the only nonhormonal version on the U.S. market—the copper IUD—can cause severe cramping and heavy bleeding. Barrier methods, meanwhile, have high failure rates.