Jennifer Gunter MD, Director of Pelvic Pain and Vulvovaginal Disorders for Kaiser Permanente in San Francisco, answered some frequently asked questions for Healthline regarding emergency contraception.

What forms do emergency contraceptive come in?

The most common form of emergency contraception is a pill, also commonly known as Plan B. It is the synthetic hormone levonorgestrel (related to progesterone, which is a natural hormone). It is best taken within 72 hours of unprotected intercourse.

A copper intrauterine device, or IUD, can also be inserted as a form of emergency contraception if inserted within five days of unprotected intercourse. Unlike other types, it also can provide 10 years of contraception from the insertion date.

A newer form of emergency contraception as a pill was approved last year by the Federal Drug Administration. This pill contains ulipristal acetate and is marketed under the name Ella. Ella is effective at preventing pregnancy up to five days after unprotected intercourse. Ella is believed to me more effective than Plan B. 

How do the different types emergency contraception work?

Both Plan B and Ella work by inhibiting ovulation: no egg, no pregnancy. The copper IUD works by affecting the sperm. 

How effective is emergency contraception?

Plan B is 88 percent effective at preventing pregnancy, Plan B is 95 percent effective when taken within 24 hours unprotected sex, and loses some efficacy each day.

Ella is more effective than Plan B (more than 95 percent), and does not become less effective over the 5 days. 

Inserting a copper IUD is 99 percent effective at preventing pregnancy.

How long after sex can the pill still be effective?

Plan B is best taken within three days after unprotected sex, but ideally in the first 24 hours. Ella can be taken anytime in the five days after sex. A copper IUD can be inserted within five days of unprotected sex.

Where can you obtain it?

 A copper IUD must be inserted by your doctor (gynecologist or family doctor) or nurse practitioner. Plan B is available over-the-counter for women ages 17 and older. Ella needs a prescription.

Can anyone buy it, or are there age restrictions?

A copper IUD and Ella have no restrictions by age, but you need to have an office visit for IUD and at least a phone call to your doctor to get Ella as it needs a prescription. Plan B is available without a prescription if you are over the age of 16, but people younger than that require a prescription. Ella is more expensive than Plan B.