We asked experts how it works, when you should take it, how much it costs and more.
Emergency contraceptives like Plan B, also known as the morning-after pill, are a safe and effective way to prevent pregnancy after unprotected sex. They are legal nationwide, though they can be easier to access in some states than in others.
How does it work?
There are two main types of oral emergency contraception.
One is a pill that contains levonorgestrel, a type of synthetic hormone. It is perhaps best-known by the brand name Plan B One-Step, but other types of emergency contraceptives with levonorgestrel include AfterPill, My Way, Next Choice One Dose and Take Action.
These types of pills work primarily by stopping the ovaries from releasing an egg, said Dr. Alison Edelman, a professor of obstetrics and gynecology at Oregon Health & Science University in Portland. They should be taken within 72 hours after having unprotected sex.
Another type of pill, known by the brand name Ella, contains the drug ulipristal acetate. It works primarily by delaying the release of an egg from the ovaries, Dr. Edelman said. It can be taken up to 5 days after having unprotected sex.
Both these types of emergency contraceptive pills have been shown to reduce the risk of pregnancy, though Ella is more effective than Plan B. In clinical trials for Ella, pregnancy rates for users ranged from 0.9 percent to 2.1 percent, while pregnancy rates for levonorgestrel-based options ranged from 0.6 to 3.1 percent.
The sooner you take an emergency contraceptive after unprotected sex, the more effective it is likely to be, said Dr. Monica Woll Rosen, an obstetrician-gynecologist at the University of Michigan Medical School.