What Happens To Your Body When You Take The Morning After Pill

Accidents happen. That's why it's critical to understand what really happens to your body when you need emergency contraception. The morning after pill side effects have been mythologized and misunderstood for long enough. It's time to break down what Plan B (and its generics) does to your body.

Emergency contraception is birth control that can be taken after accidental or unplanned unprotected intercourse when pregnancy is not desired," Dr. Katie Bolt, an OB/GYN at Partners in OB/GYN Care at Texas Children’s Pavilion for Women in Houston, tells Bustle. "Plan B One Step, Take Action, My Way or AfterPill are all types of emergency contraceptive pills that contain the medication levonorgestrel which is a type of hormone. If this is taken within three days of unprotected intercourse, it can decrease your chance of pregnancy by up to 89 percent. It can be taken up to five days after intercourse, but is most effective when taken as soon as possible." Of course, there are other options for emergency contraception, like IUD implantation (expensive but the most effective), or a pill called ella, but the morning after pill is by far the most convenient — since it's so readily available.

But how does it work, exactly? "It works by mainly by stopping the release of an egg from the ovary. It may also work by preventing fertilization of an egg (the uniting of sperm with the egg) or by preventing attachment (implantation) to the uterus," Diana Ramos, MD, Chair of the National Preconception Health and Health Care Initiative, tells Bustle. Every body will react to this pill in different ways, but there are some things to look out for.

Here are nine ways that the morning after pill does (and doesn't) affect your body, according to experts.

1You May Have Delayed Ovulation

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This seemingly small step is actually the key to how the morning after pill works. "The morning after pills with levonorgestrel are effective at preventing pregnancy by delaying ovulation ... If ovulation is delayed by the levonorgestrel effect, then the sperm that may be present after unprotected intercourse will not have the opportunity to fertilize an egg, thereby preventing pregnancy," Dr. Bolt explains. It can be confusing to understand how the morning after pill works, but this is something to take note of.

2Your Endometrial Lining Might Change

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Levonorgestrel may sound like the name of a spell, but it's basically just a form or progestin (which is active in many hormonal birth controls). And progestin is a synthetic that acts similarly to the naturally-occurring progesterone (which regulates your uterine lining).

"[One] side effect of taking this progesterone hormone is that it may affect implantation, which is a bonus as an emergency contraceptive." Dr. Sheila Loanzon, MD tells Bustle. This works because Plan B changes the lining of the endometrium, Dr. Loanzon says, which also contributes to preventing pregnancy.

3Your Period Might Be Delayed

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There's no cause for alarm if you don't get your period after taking emergency contraception. "Because Plan B delays ovulation, this may result in changes in your menstrual cycle [like] your cycle starting earlier or later than usual," Dr. Loanzon says. "This can cause anxiety; however, as long as you have a negative pregnancy test, this is reassuring." The fact that you can take Plan B any time of the month is amazing, but when you take it will affect side effects.

"Shortly after taking it, you may or may not have a period, this is because depending on where you are in your menstrual cycle will determine if you have a period," Dr. Ramos says. So don't freak out, and keep a pregnancy test (or three) on hand in case you need reassurance.

4Or You May Have Other Changes To Your Cycle

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A slight delay is not the only thing that can happen to your period after taking the morning after pill. "You may also see unpredictable spotting before the actual menstrual cycle," Dr. Bolt says. "The point is, not to worry if there are abnormalities in your cycle following the morning after pill. You should expect menstrual fluctuations and with time, the cycle should normalize again. If you do not have a menstrual cycle within 3 weeks of taking the morning after pill, take a pregnancy test." Spotting, or breakthrough bleeding, is a really common side effect with non-emergency birth control as well. Just keep an eye on it and you should be quite alright.

Dr. Philip Chenette, member of Progyny's Medical Advisory Board, tells Bustle that "ten percent of women experience an unusual menstrual flow after using Plan B." So, bleeding or not, you're likely in the clear.

5You May Get Nauseous

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No one likes throwing up. But, if you're scared about pregnancy (and, perhaps, morning sickness), it's good to know that the nausea you're feeling could also be from the morning after pill. "Most common side effects from taking Plan B are nausea, vomiting, and irregular bleeding," Dr. Loazon says. So you don't need to panic if you start to feel queasy. You just have to be cognizant of when you're throwing up, just in case.

"Around one in five women experience nausea and half those experience vomiting," Dr. Chenette says. "[But] vomiting within a few hours of taking Plan B will reduce its effectiveness." Because of this, Dr. Ramos advises, see your health care provider immediately if you throw up the pill. They can help get you some medicine to keep from throwing up more. And if it's mild nausea without vomiting, there's a luckily a bunch of remedies you can try at home.

6You Won't Have Terminated A Pregnancy

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This is crucial. If you take Plan B, you won't be ending a pregnancy. "Plan B is not the same as an abortion," Sonia Patel, Pharm.D., Chief Pharmacist at Capsule tells Bustle. "An abortion, whether through medicine or a procedure, refers to terminating a pregnancy by detaching a fertilized egg from your uterine lining. Plan B’s main aim is to prevent that fertilization from happening in the first place. To reiterate, Plan B won't work if you're already pregnant." This means that if you happen to have already gotten pregnant, you'll need to see a doctor and explore other options. And if you're not, you'll likely stay that way.

7You Won't Harm Your Baby If You're Breastfeeding

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If you're already a parent, you can still take Plan B. Emergency contraception will not hurt your baby. "Even [people] who are breastfeeding can take levonorgestrel emergency contraception," Dr. Bolt says. "It may cause a brief decrease in milk production, but it does not harm the breastfeeding baby." This is really important to know, since you definitely don't need more on your plate. You're already caring for a new human life right now.

8You Might Experience Drug Interactions

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Plan B is available over the counter, but that doesn't mean it's always a good idea to take it without consulting a medical professional first. "[Plan B might not be as effective] if you’ve taken certain drugs (including barbiturates, St John's wort, and certain HIV/AIDS medications), so check with your pharmacists about medication interactions," Dr. Patel says. Even if you don't think your prescriptions or supplements are on this list, check anyway. It's always better to be safe than sorry.

9You Likely Won't Have Long-Term Effects

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Above all else, know that you're likely safe taking emergency contraception. "The hormone in Plan B is metabolized relatively quickly and has not been shown to have any long-term impact on health, even when taken multiple times," Bat-Sheva Lerner Maslow, MD, a reproductive endocrinologist at Extend Fertility tells Bustle. The only things that will be unpleasant in the long-term if you take Plan B multiple times are the immediate side effects, like nausea, and the chance of pregnancy. "Plan B is not as effective as condoms or birth control pills when used according to directions, so don’t use Plan B as routine contraception," Dr. Chenette says.

If you have any side effects that are particularly alarming, or unusual, always make sure to contact a doctor. But, in most cases, the morning after pill is a well-regulated, safe option if you need emergency contraception. "The morning after pill is simply a pill that you swallow as soon as possible after unprotected sex," Dr. Bolt says. "It is easily accessible at your local pharmacy. It is even available on Amazon.com with prime shipping so that you can have it sent to your home inconspicuously in 2 days. You could even buy one to keep in your bathroom for when (not if) accidents happen." Just be safe, have fun, and know your body.