The study, which was published in The Endocrine Society's Journal of Clinical Endocrinology & Metabolism, followed 1,045 healthy Chinese men between the ages of 20 and 45, according to EurekAlert. Every man had fathered a child in the two years before the study and their female partners did not have fertility problems.

For thirty months, the men were injected with 500mg of testosterone undecanoate in tea seed oil once a month. The treatment was 99 percent effective at preventing pregnancy, and after the study ended all but two of the men had their fertility levels return to normal.

"For couples who can not, or prefer not to use only female-oriented contraception, options have been limited to vasectomy, condom and withdrawal," said Dr. Yi-Qun Gu, MD, of the National Research Institute for Family Planning in Beijing, China. "Our study shows a male hormonal contraceptive regimen may be a potential, novel and workable alternative."Gu said more testing was needed to determine the long-term effects of the injections on men's hearts and prostate glands, reports The Telegraph.

Scientists have been trying to develop a male Pill for almost two decades, but progress has been slow. Last month, in a study published in American Journal of Human Genetics, researchers said they had identified a gene called CATSPER1 that allows sperm cells to dig into the egg to fertilize it, according to iT Wire. Scientists theorized that a drug that targeted healthy versions of the gene could lead to an effective male Pill. However, large pharmaceutical companies have been reluctant to perform large trials and many people believe that women wouldn't trust men to take the pill.

Injectable Testosterone May Provide Effective Male Contraception [EurekAlert]
Hopes For A 'Male Pill' Could Be Resurrected [The Telegraph]
Male Birth Control Pill Closer With CATSPER1 [iTWire]

Earlier: Would You Trust A Guy Who Said, "It's OK, I'm On The Pill?"
Why Is There No Sperm-Killing Birth Control Pill?

One study showed a 98 percent success rate in couples using a hormone male contraceptive, Bremner said. Side effects include weight gain and acne.

However, there's one small problem: The doctors are having trouble getting pharmaceutical companies on board.

"It's taking normal young men without a disease and testing a drug in them for years — that's an issue," he said. And men aren't the ones at risk of getting pregnant, which carries its own hazards, and which justified testing contraceptives in females.

Breakthrough In Male Birth Control Remains Elusive [Seattle Post-Intelligencer]