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PHILADELPHIA (CBS) – Researchers are testing out a birth control for men in the form of gel. This week the National Institutes of Health (NIH) announced the start of a trial for a male contraceptive.

The gel is called NES/T and contains progestin, a hormone that can prevent ovulation during pregnancy.

NIH says the is applied to the back and shoulders and absorbed through the skin. The progestin blocks natural testosterone production in the testes, reducing sperm production to low or nonexistent levels.

“Many women cannot use hormonal contraception and male contraceptive methods are limited to vasectomy and condoms,” said study investigator Diana Blithe, Ph.D., chief of NICHD’s Contraceptive Development Program. “A safe, highly effective and reversible method of male contraception would fill an important public health need.”

Researchers plan to enroll approximately 420 couples into the study for a year to test its effectiveness.