It's only fair that men share the responsibility of using a hormone-based birth control to prevent unwanted pregnancies. Now, new research has brought that possibility just a littler bit closer to reality. A study by researchers at Harbor-UCLA Medical Center shows that a sperm-inhibiting gel has been shown to significantly reduce men's reproductive abilities, thereby lowering the risk of impregnation. Here's what you should know about the breakthrough:

What's in the gel?
The gel, which would likely be applied using a patch, uses two types of hormones: sperm-inhibiting testosterone and a synthetic chemical called progestin, which amplifies testosterone's ability to turn off reproductive hormones. The two have been used together before in pill, implant, and shot form, but progestin was shown to have side effects like acne breakouts and fluctuations in cholesterol level, says Thomas H. Maugh II at the Los Angeles Times. In this study, researchers used a progestin synthetic called Nestorone, which supposedly doesn't cause any such side effects.

How effective was the cream?
Researchers at Harbor-UCLA Medical Center enrolled 99 men in a preliminary study, having some of them use the new gel. For 89 percent of the men who used the combo gel, their sperm counts were significantly reduced, to an average of 1 million sperm per milliliter, a level researchers describe as "compatible with very low pregnancy rates." By contrast, a control group administered only testosterone creams saw only 23 percent of its patients experience lower sperm counts.

How does the gel compare to the pill? 
Women on the pill experience pregnancy rates close to 0.3 percent per year; meanwhile, for men who use the gel, that number is nearly 10 percent, which is still way too high for effective commercial use. For now, says Cassie Murdoch at Jezebel, "we'll just have to wait until more studies are done" until we're able to "live the dream of slapping these onto the skin of every gentlemen who wants one."

Sources: Jezebel, io9, Los Angeles Times