A multinational team of researchers have finally identified and developed a molecule that can work effectively at providing reversible male contraception.

Contraception has been a hot-button issue, both for politicians and for researchers. The Centers for Disease Control and Prevention reported earlier this year that 37 percent of pregnancies in the United States are unintended. While most couples rely on female contraception, 21 percent of couples use male-reliant birth control (though that number has been reported as high as 33 percent), whether that means vasectomies, condoms, or the withdrawal method. But vasectomies are generally considered irreversible, as they are surgeries, after all, and fertility after a reversal is unreliable. Condoms and the withdrawal method can have a relatively high failure rate with typical use. That is why it seems pressing that scientists develop a method for male contraception, which they believe can lower the unplanned pregnancy rate.

The molecule is called JQ1, and it targets a specific protein called BRDT that is necessary for fertility. When administered to mice, their bodies produced fewer sperm. The sperm that the body did produce swam less effectively. The method is effective, scientists say, and when the mice stopped taking them, it did not affect their fertility or later offspring.

The problems of developing a male version of reversible contraception have been numerous. As the University of Washington's William Brennan says in his accompanying commentary of the study, such obstacles include "the amazing numbers of spermatozoa produced by normal men, 1,000 per [heartbeat]…the difficulty of fully suppressing these millions of spermatozoa produced daily compared to the relative ease of preventing the production of one ovum per month in the female…concern that affecting production of cells in the germline could alter the genetics of offspring, and…the fact that much of spermatogenesis occurs 'behind' the blood-testis barrier (analogous to the blood-brain barrier), which prevents access of many molecules, especially larger ones, to most of the cells in the seminiferous tubules."

However, JQ1 seems to have surmounted all of those hurdles.

In addition to this study conducted by researchers from Houston and College Station in Texas; Boston; Oxford in England; Ontario; and in Washington, DC; a study last year found that inhibiting retinoic acid, or Vitamin A, receptors inhibited the creation of sperm.

In a statement, Martin Matzuk from Baylor College in Houston, one of the study authors, quipped, "This is a good reason to get excited about low sperm counts."

If the results are applicable in humans later, the only question remains is if men would want to take contraception themselves.

The study was published in Cell journal.