Another tool for the prevention of unintended pregnancy has recently been approved by the FDA: ulipristal acetate (marketed under the brand name ella®), a type of emergency contraception that can be taken up to five days after unprotected sexual intercourse. The medication is already in use in Europe, and the FDA conducted its own clinical trials before approving it as a prescription contraceptive on August 13. Ella was found to be safe and effective, and better at preventing pregnancy than current forms of emergency contraception, such as Plan B.

While Plan B can be taken up to three days after unprotected intercourse, its effectiveness is dependent upon how soon it is taken after sex. Plan B taken immediately after unprotected intercourse is more effective than when it is taken three days afterward. Ella, on the other hand, has been found to be just as effective on the fifth day as it is on the first day. According to the New York Times:

Women who have unprotected intercourse have about 1 chance in 20 of becoming pregnant. Those who take Plan B within three days cut that risk to about 1 in 40, while those who take ella would cut that risk to about 1 in 50, regulators say. Studies show that ella is less effective in obese women. 

Ella works by the same mechanism by which hormonal birth control pills work: by suppressing ovulation. It does this by delivering a synthesized version of progesterone, a hormone that women produce naturally in their own bodies.

During the menstrual cycle, the levels of three hormones (estrogen, follicle stimulating hormone, and luteinizing hormone) slowly increase, and when they reach a certain point a ripened ovum is released by the ovary. The follicle starts to produce more progesterone, while the ovary continues to secrete estrogen. If the ovum is fertilized during this time, and the resulting zygote implants itself into the uterus, the body continues to produce progesterone. This uninterrupted production of progesterone blocks the ebb and flow of hormones regulated by the menstrual cycle. Once someone is pregnant, ovulation ceases, which ensures that one pregnancy is not usurped by a subsequent one.

Pregnancy is mimicked by the hormone levels provided by contraceptive pills. By increasing the level of progesterone, the body is “tricked” into thinking it is already pregnant, which suppresses ovulation. When ovulation is suppressed, there are no eggs to be fertilized and therefore pregnancy does not occur. In addition to preventing ovulation, hormonal contraceptives (including emergency contraception) also thicken the mucosa in the reproductive tract, which, on the off-chance that ovulation does occur, will help prevent fertilization by impeding the sperms’ ability to reach the ovum.

Planned Parenthood is pleased with the upcoming inclusion of ella in an expanding arsenal of effective contraceptive options. “Ella, or UPA, is safe and effective at preventing ovulation and therefore pregnancy in the five days after unprotected intercourse,” says PPFA Vice President for Medical Affairs Dr. Vanessa Cullins. “Given the fact that half of all pregnancies in the U.S. are unintended, it is vital that women have an array of choices available to prevent unplanned pregnancy.”

Ella will be on the market in late autumn of this year. Until then, Plan B is available at Planned Parenthood clinics and other pharmacies. Those above the age of 17 can obtain it over the counter, while anyone below the age of 17 needs a prescription.