How effective is emergency contraception at preventing pregnancy?

The effectiveness of emergency contraception depends on what type you use and on how soon you take it. We’ll give you the basics here, but there’s more to read from the EC experts.

If you’re taking Plan B One-Step, Next Choice, or using the Yuzpe method (which means taking a combination of some birth control pills), the quicker you take it after unprotected sex, the more effective it is. We repeat: the sooner, the better. You can take it for up to 5 days, but within 3 days is better, and within 24 hours is the best yet. (That’s all the more reason to get some and have it around, just in case.)

Progestin-only pills—which includes Plan B One-Step and Next Choice—are more effective than EC pills with both progestin and estrogen (aka “combined” pills). Both types will reduce your chances of an unplanned pregnancy, but if you can get your hands on a progestin-only method, then take that.

There’s a new oral EC that hit the market in the U.S. in December 2010, called ella. You can use ella for up to five days and unlike the other types of oral EC, it’s as effective on day five as it is on day one. Just be sure to use it within five days!

Finally, if you get a Paragard IUD inserted within five days after unprotected sex, it will lower your chance of pregnancy by 99.9%.