Getty Images

When it comes to preventing pregnancy, the burden falls largely on women. But that responsibility could soon shift, according to new research from Columbia University that raises the tantalizing prospect of a male birth control pill.

The key to a pill for men may lie in vitamin A, which is necessary for the growth of sperm cells. When researchers working with mice administered an experimental medication that interfered with receptors needed to metabolize vitamin A, male mice lost their fertility. Shortly after the animals stopped taking the compound, they resumed mating and making babies successfully.

(More on Time.com: Could a New “Viagra Condom” Encourage Safer Sex?)

It’s been more than half a century since the Pill emerged on the reproductive scene, upending sex as we knew it. It was simple and effective, giving women the ability to take control of their fertility. Last year, on the fiftieth anniversary of the pill, a TIME cover story lauded the pill as “the means by which women untied their aprons, scooped up their ambitions and marched eagerly into the new age.”

A male birth control pill wouldn’t have quite the same societal resonance, of course, but it would allow men and women to share more evenly the burden of medical contraception — as well as any attendant health risks. For the Columbia researchers’ experimental drug, toxicologists noted no side effects.

It’s certainly conceivable, however, that side effects seen in mice can vary considerably from those that may affect men. Vitamin A receptors tend to have at least subtle side effects, says Dr. Peter Schlegel, professor and chair of urology at New York Presbyterian Hospital and Weill Cornell Medical Center.

“Fatigue is not something a rodent is going to talk about,” says Schlegel. “Stopping 100 million sperm from being made each day is likely to have some crossover effect in some other areas of the body. That said, this is some of the cleanest data I’ve seen in terms of male contraceptives.”

(More on Time.com: FDA Reviews Popular Birth Control Pills for Blood Clot Risk)

Given that about half of all U.S. pregnancies are unintended, despite the availability of dozens of formulations of oral birth control for women, plus any number of other female contraceptive options, there is plenty of room for a new birth-control method for men. Currently, men have just two main choices: condoms or vasectomies.

Would men even be willing to take a pill? “If it doesn’t affect sexual function and it’s reversible, yes,” predicts Schlegel.

The Columbia researchers aren’t the first to pursue a male birth control pill (see here and here). But their approach may be somewhat more promising. Previous research on male contraceptives has mostly involved hormone treatments, which have potential side effects like loss of sex drive and prostate problems, and typically have to be administered by injection rather than a pill. They also tend not to work equally well in all men. Many past attempts at male birth control have thus fallen short.

The Columbia scientists think their results could lead to the development of a pill for men without the side effects and problems of a hormone-based drug. But the compound will have to undergo further testing to prove safety and effectiveness and be validated in human clinical trials before it could be made available. The process could take years.

(More on Time.com: An Argument for Making Birth-Control Pills Available Over the Counter)

It’s purely coincidence that the drug being investigated was even discovered. Scientists have been aware of vitamin A’s association with sterility for a century, but incorporating a compound that affects vitamin A into a contraceptive pill is not so easy. Vitamin A is crucial for vision and the immune system, and isolating the appropriate component of action has taken time.

In 2004, the study’s senior author, Debra Wolgemuth, a professor of genetics and development and a professor of obstetrics and gynecology at Columbia, learned that the pharmaceutical company Bristol-Myers Squibb had abandoned work on a compound called BMS 189453 after determining it was a “testicular toxin,” code for: it caused infertility. Wolgemuth’s team decided to give it a look.

“We were intrigued,” Wolgemuth said in a statement. “One company’s toxin may be another person’s contraceptive.”

(More on TIME.com: Who’s Using the Morning-After Pill?)

The new study published this month in the journal Endocrinology.