How Does The Morning After Pill Work? 8 Things To Know About Emergency Contraception

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For so many reasons, it's a super positive thing that emergency contraception, AKA the morning after pill, exists. But like so many aspects of reproductive healthcare, getting really thorough information on what it is, how it works, what increases or decreases effectiveness, and what might happen to your body when you take it, can be a little hard to come by. Getting all the facts about emergency contraception is super important when making informed choices about your sex life.

As for how emergency contraception pills work, they interfere with the hormone patterns necessary for a pregnancy to occur, Dr. Savita Ginde, a Denver based physician, tells Bustle.

"Most work in the first 72 hours, but preferably 12, in one of three ways: temporarily stopping the release of an egg, stopping fertilization, or preventing a fertilized egg from attaching to the uterus," Dr. Ginde says. "Most manufacturers are using hormones similar to those found in low dose birth control pills. Ella, a newer product, claims effectiveness up to 5 days."

Additionally, it is also really important to remember that emergency contraception is not an abortion pill, Dr. Ginde says, so it has no impact on pregnancy if you are already pregnant.

"EC is a last line of defense to prevent pregnancy," Dr. Ginde says.

Take a look below to get a little more thorough on all things emergency contraception.

1. Time Is Really Key When It Comes To Effectiveness

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It's all about timing, my friends. Taking it within 72 hours is the general rule, but the sooner the better.

"Time is the key component to the effectiveness of emergency contraception pills," Dr. Ginde says. "This family of contraception doesn’t disrupt pregnancy, therefore it must be taken prior to pregnancy occurring."

2. It Could Be Less Effective For People Above A Certain Weight

Typically, most emergency contraception is not dosed for women over 175 lbs, meaning people who weigh over 175 pounds may metabolize it in a way that negatively affects its effectiveness.

The effectiveness of some pills goes down in relation to weight, Dr. Ginde says. Your healthcare provider or a pharmacist can help select the best manufacturer for you.

In a study published in Contraception, Alison Edelman, M.D. and a team at Oregon Health and Science University showed that women who had BMIs between 35.9–46.7 had about half the levels of EC in their bloodstream than women in the range below them. Other studies done at places like Columbia University and the University of Edinburgh have shown the same results. Researchers at University of Edinburgh found that the emergency contraception pill ella was more effective for women with a higher BMI than Plan B.

The very fact that it is difficult to find thorough information or definitive answers as to the effectiveness of EC is an example of medical bias against fat people. Finding a fat-positive doctor can be a place to start when getting the best medical care for your body type.

Additionally, IUDs are an example of emergency contraception that are effective regardless of weight, Dr. Ginde says. According to Planned Parenthood, you can get a copper IUD installed up to 5 days after you have unprotected sex, and it can act as EC, and then as a more longterm form of birth control.

3. Side Effects Can Really Vary By Individual

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If you've taken EC before, it's very likely that you might have had some side effects that came along with it.

"The most common side effect of EC is a temporary change in your period," Dr. Erin Burke, PhD, Modern Fertility's head of clinical research, tells Bustle. "You might have spotting, an irregular, or heavier period after taking it."

Some people also often experience nausea, abdominal pain, and feel tired after taking emergency contraception, she says.

Often people will get a period within a week or two of taking the pill, and it usually returns to normal from there. If it doesn’t, it’s not a bad idea to take a pregnancy test to rule out pregnancy, Dr. Burke says.

And since all bodies are unique, your body might react differently, so if these or any symptoms continue for more than a week, definitely see your doctor.

4. Emergency Contraception Doesn't Make You Infertile

We often hear people wondering if taking EC can make them infertile, but that's not the case, Dr. Burke says.

"Taking Plan B does not impact a woman’s fertility in the long-term, though this misconception is quite commonly held," Dr. Burke says. "We recently ran a survey that looks at information gaps in fertility, and found that 42% of women were not aware that taking hormonal birth control (for example, pill, patch, IUD) for more than five years does not reduce a woman's fertility."

5. It Only Works For One Instance Of Unprotected Sex

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The morning after pill is good for one use, meaning that it will not protect you from pregnancy in future cases of unprotected sex.

"EC pills are meant to prevent pregnancy for one instance of unprotected sex," Christine Yu, tells Bustle. "Another [instance of an] unprotected sex act may lead to pregnancy if ovulation occurs."

6. It's Important Not To Assume EC Worked Just Because You Took It

Again, there are some factors that contribute to effectiveness of the pill. While you don't want to get super worried after you take it, don't assume that it's automatically worked.

"The only way to confirm if EC worked is having a next menstrual period," Yu says. There are also times of the month, in relation to your cycle of ovulation, where the morning after-pill might not work. If your period is late or seems off schedule somehow, check in with your healthcare provider.

7. Some Women Need to Be More Cautious When Taking It

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It's true that there are individual health and lifestyle factors that can impact what happens when taking EC.

"Women with a known hypersensitivity or allergic reaction to progestins should not take it," Dr. Danielle R. Plummer, PharmD, tells Bustle.

Women who smoke should use caution due to an increased risk of cardiovascular disease, says Dr. Plummer, as do those with a history of breast cancer, and those with conditions that are made worse by fluid retention like migraines, asthma or epilepsy.

However, since this is a one-time dose, Dr. Plummer says it is still considered safe in many women who cannot take long term oral birth control. For a more thorough understanding of how EC can impact you and your particular lifestyle factors or health conditions, it's important to discuss your situation with a trusted healthcare provider.

8. You Don't Want To Rely On EC As Your Go-To Birth Control Method

"Taking as often as needed is safe, however, it’s called emergency contraception for a reason," says Dr. Ginde. "You don’t want to rely on them as your go-to method of birth control."

This is in major part because of how unpleasant the side effects can be, like bleeding and nausea. They are also less effective than more consistent forms of birth control.

"If you find yourself using them more than a couple of times, talk with your provider about the many, more effective, forms of birth control that can be used on a regular basis," says Dr. Ginde.

Again, being as informed as possible when it comes to your sex life and health is both necessary and empowering. If you have any more questions about the best way to approach birth control if that needs to be a part of your plans, talk to a trusted and informed healthcare provider to begin your research.