On Tuesday, FDA approved the first birth-control pill for continuous use that will stop a woman monthly menstrual period indefinitely.

The new contraceptive, Lybrel, comes in a 28 day-pill pack with low-dose combination tablets that contain 90 micrograms of a progestin, levonorgestrel, and 20 micrograms of an estrogen, ethinyl estradiol, which are active ingredients available in other approved oral contraceptives. Continuous contraception works the same way as the 21 days on-seven days off cycle. It stops the body's monthly preparation for pregnancy by lowering the production of hormones that make pregnancy possible.

The continuous contraception is the first made to put off periods altogether when taken without a break. Standard birth-control pills have a 21-days-on, and a 7-days-off regimen that are placebos or pill-free.

The safety and efficacy of Lybrel as a contraceptive method were supported by two one-year clinical studies, enrolling more than 2,400 women, ages 18 to 49. Health care professionals and patients are advised that when considering the use of Lybrel, the convenience of having no scheduled menstruation should be weighed against the inconvenience of unscheduled bleeding or spotting.

Sales of Lybrel by New Jersey-based Wyeth will start in July.