woman holding pill in her hand

The Facts About Emergency Contraception

Carolyn Westhoff, MD

Carolyn Westhoff

Emergency contraception has been available for decades, but interest has skyrocketed since the U.S. Supreme Court’s decision to overturn the constitutional right to an abortion.

“Emergency contraception is safe, effective, and anyone can use it,” says Carolyn Westhoff, MD, a gynecologist and researcher at Columbia University Vagelos College of Physicians and Surgeons. “And in this day and age, emergency contraception is particularly important for women who have the poorest access to reproductive health care.”

We recently spoke with Westhoff to learn what people should know about the options, how to best use emergency contraception, and myths surrounding the medications.

Emergency contraception is not the abortion pill.

Emergency contraception is usually a medication, a pill that is taken within a few days after unprotected intercourse to prevent pregnancy.

In contrast, the abortion pill is used after a positive pregnancy test and can be used in the United States up to the 10th or 11th week of pregnancy.

Two types of medications can be used for emergency contraception.

Many brands of emergency contraception contain a hormone called levonorgestrel, which is also used in many regular birth control pills. In the United States, levonorgestrel options (including Plan B), are available to anyone over the counter, with no need for a prescription.

Another type of pill (brand name ella) uses a different drug called ulipristal acetate.

Both types prevent pregnancy primarily by preventing ovulation, when an egg is released from the ovary.

Timing matters.

Emergency contraception works better the sooner it’s used. Though levonorgestrel can prevent a pregnancy up to three days after unprotected sex and ulipristal can prevent a pregnancy up to five days afterward, do not delay if you have the pills on hand.

To understand why, you need to understand a few things about biology. The greatest chance of getting pregnant occurs with unprotected sex a few days before ovulation. In that case, the sperm will already be right there waiting in the tube when the egg emerges from the ovary.

Emergency contraception delays ovulation by several days, so that by the time the egg finally emerges, the sperm is no longer capable of fertilizing the egg.

Emergency contraception does not work after ovulation has already occurred. The longer you wait to take emergency contraception after unprotected sex, the less likely it is to help because it's possible that ovulation has already occurred.

Ulipristal is more effective, but less accessible.

Levonorgestrel is readily available over the counter, but ulipristal is more effective and it can be used five days after unprotected sex, later than levonorgestrel. With ulipristal, you get another day or two because the drug can still prevent ovulation even after the process has started. That’s because ovulation is a multi-step process.

Very importantly, ulipristal has greater effectiveness than levonorgestrel among women weighing 165 pounds or more. I’ve studied the two drugs, and they behave differently in heavier women. Women over 165 pounds get only about half the drug level that a woman weighing less gets. Weight doesn't make any difference with ulipristal; the drug levels are the same. The difference is because the drugs are metabolized by different pathways.

IUD insertion is the most effective form of emergency contraception.

The IUD can be a really fabulous choice for emergency contraception. And we've got a lot of data showing IUDs are extremely effective, around 99%, whereas pills are more in the range of 80% to 90% effective.

So it's a shame that more people don't know it's one of their alternatives. It's just a little harder to organize getting an IUD within five days of unprotected sex than getting a pill.

Studies show that women who get an IUD for emergency contraception are generally very happy with it and very happy to continue using it for ongoing contraception.

Stock up in advance.

It’s more important than ever to have emergency contraception on hand in advance, especially for women in states where access to all reproductive health care is so poor.

It’s especially important to have on hand if choosing ulipristal, which is only available by prescription and not stocked in many pharmacies in the United States. Even in pharmacies that do carry it, it’s often not in the store on the day you come in, which is a problem for a treatment that needs to be taken as soon as possible.

Unprotected sex is common, and I think people don't take emergency contraception anywhere near as often as they should. Most of the time if you have unprotected sex, you're going to get away with it. With two fertile people, the chance of pregnancy from a single unprotected act of sex is only about 8%; therefore, people often just cross their fingers. But that's not a good long-term strategy. Using emergency contraception can lower that pregnancy risk to about 1%. 

It’s OK to use emergency contraception multiple times.

There's absolutely no medical danger in taking emergency contraception over and over again. And access to or use of emergency contraception doesn’t encourage women to have unprotected sex. In the long run, using an ongoing contraceptive method is more effective, less expensive, and more convenient than emergency contraception, but it doesn't matter how often emergency contraception is used.

When I write prescriptions for emergency contraception, I put in the option for multiple refills.  We know that people taking the birth control pill forget sometimes, and we know very well that forgetting the pill often happens more than once. Most people are not perfect pill takers; studies show that is true for everybody, including men and even male physicians. So, it's good to have emergency contraception on hand.

Emergency contraception pills are safe, even for women who can’t use birth control pills.

Both types of oral emergency contraception are totally safe for anybody, even women who wouldn't normally use a birth control pill because of medical contraindications. The hormone in emergency contraception is in the body for just one day and does not pose any risks.

The side effects are modest. Decades ago, emergency contraceptives contained very high doses of the drug that could make you feel pretty sick. With the current formulations, some people who are generally sensitive to pills might briefly have an upset stomach, feel tired, get headachy, but it's very hard to tell if that's a coincidence or a direct effect of taking the drug. But these reactions are infrequent and minor.

Even if the drug is making you nauseated, the drug will be absorbed from your stomach in 20 or 30 minutes. Only if you vomit within the first 15 minutes of taking the pill would we advise a second dose.


More information

Carolyn Westhoff, MD, is the Sarah Billinghurst Solomon Professor of Reproductive Health in the Department of Obstetrics & Gynecology at Columbia University Vagelos College of Physicians and Surgeons and professor of population & family health and epidemiology at Columbia University Mailman School of Public Health.

Her work focuses on improving quality of and access to contraceptive and abortion services. She has published over 300 scientific articles relating to safety and effectiveness of contraception and abortion. As a member of National Institute of Child Health and Human Development's Contraceptive Clinical Trials Network, she develops new contraceptives using novel pharmaceutical agents.