morning after pill pregnancy

How Does The Morning-After Pill Work?

Dr. Jolene BrightenPublished: Last Reviewed: Birth Control Leave a Comment

The Morning-After Pill or Plan B is a medication that comes with a lot of confusion, including how the morning-after pill works. So, let me clear it up straight out the gate—the morning-after pill works by preventing ovulation. Perhaps the worst part of not knowing how the morning-after pill works is that typically, you have to make a decision about it when you are the most stressed and pressed for time.

Confused about your options if you’ve had unprotected sex or the condom failed? You’re not alone. 

Surveys show that up to 40% of women in the US and Europe feel completely in the dark about what the morning-after pill is, how it works, and where to get it.

What’s worse is according to the Guttamacher Institute, only 17 states in the United States requires medically accurate sex education and 19 states require that contraception information is included. Houston—we have a problem!

This is why I am hosting the Take Back Your Hormones Conference. I want women to get the information we all deserve to know about our bodies and the real talks on baby making and birth control. It's free to attend November 4th-8th, 2019.

We are so fortunate to live in a time where access to birth control and emergency contraception is widespread. But despite the improvements we’ve made, so many women still encounter judgment, shame, and harassment when seeking ways to prevent pregnancy. 

Especially when it comes to oral emergency contraception, there is so much confusion and misinformation out there.  

And there’s never been a placebo-controlled trial of it due to valid ethical concerns for the women in the placebo group — which doesn’t help the lack of quality scientific data available.

Look, mistakes happen. And heaven knows we’ve all made bad choices a time or two! If you’re reading this because you’ve had unprotected sex, don’t beat yourself up — know your options and make choices based on evidence, not rumors and fear-mongering. 

In this article, I’m going to break down the myths surrounding emergency contraception and give you all the details I possibly can, so you can make informed choices.

The Morning After Pill – What You Should Know:

  • Plan B or The Morning-After Pill is not an abortifacient
  • This medication works to prevent ovulation
  • Most versions are available over-the-counter
  • You need to use it within 72 hours in most cases (sooner the better)
  • It should not be used as your primary means of pregnancy prevention
  • There are no studies to show averse outcomes if you are unknowingly pregnant and use it
  • Because it prevents ovulation, symptom of hormone imbalance may arise
  • There are short term side effects that you should review with your pharmacist or doctor

When should I use the morning-after pill?

The morning-after pill was designed to be used as a stop-gap measure to prevent pregnancy after unprotected sexual intercourse. 

I’m going to list a number of reasons you may require to use the morning-after pill and not one is meant to shame you or open up a “case of the judgies” from anyone reading this. If you feel the need to judge or hate on another woman then I ask you redirect your energy into providing supporting women through better education. If you’re here, I trust you are wanting to create positive change that ensures the healthy existence of our species.

It is best used in the following circumstances:

  • The condom broke
  • You forgot to take your birth control pill or get your shot
  • You haven’t actually been using a regular method of birth control
  • You’ve been tracking your fertile window and thought you were in the clear — and then realized maybe you weren’t
  • You didn’t use a condom
  • You accidentally used the wrong type of lube with a condom — water and silicone-based lubes work best with condoms; oil-based lubes can compromise them
  • Your partner was supposed to pull out but didn’t — or at least not in time
  • You realized your IUD had become expelled after you had sex
  • You’ve been raped
  • You were under the influence and not sure if a barrier was used 

How does the morning-after pill work?

Plan B or the morning-after pill is not an abortifacient. Or in other words, it doesn’t cause a fertilized egg to be expelled from your body. Its job is to prevent ovulation and therefore prevent fertilization.

The morning-after pill is known by several different names:

All of them, with the exception of Ella®, are made with the drug Levonorgestrel (LNG) and is a progestin. Ella® is the drug ulipristal acetate (UPA) and is known as a selective progesterone receptor modulator. 

Both of these medications work to prevent pregnancy by delaying ovulation — so if your egg doesn’t get released, it can’t be fertilized. While sperm can hang around inside you, alive, for several days, they eventually die before ovulation occurs.

UPA is considered the more effective of the two options, but it does require a prescription from a medical professional in order to obtain it. But, that also means you may be able to get it approved for insurance coverage. LNG is available at pretty much any drugstore over the counter and with no age restrictions.

How effective is the morning-after pill?

If taken properly, within 72 hours of unprotected sex (but the sooner the better) — LNG boasts an efficacy rate of 85-97%

UPA is indicated for use up to 120 hours after the unprotected sexual encounter. This medication is as effective on day 5 as it on day 1 — so it’s a little more flexible than LNG. In studies where they’ve been evaluated together, UPA had a slightly higher success rate of 86-98%.

Of note — if you happen to vomit within 3 hours of taking the pill, it may be rendered useless and you should consider trying another dose.

It is not as effective as using regular birth control, so it makes the most sense to use other methods on a regular basis and only consider reaching for the morning-after pill in cases of emergency. 

Because this medication works by inhibiting ovulation — if you’ve already ovulated — pregnancy is more likely to occur. To a certain extent, LNG and UPA may cause the uterine lining to thicken and thereby inhibit sperm from joining an egg…but it’s just not as foolproof a tactic as preventing ovulation in the first place. 

How do you take the morning-after pill?

Emergency contraception can be taken at any time during the menstrual cycle. 

Ideally, it should be taken as soon as possible after the unprotected sexual encounter happens. 

Generally, pills containing LNG are most reliable when taken within 24 hours. UPA is most effective when taken within 5 days.

What happens if I take the morning-after pill, then have sex?

In theory, nothing would interfere with the morning-after pill from working if you take it first, then have unprotected sex. 

However, these drugs are meant to work within a very specific time frame…so by taking it before the sexual encounter, you are cutting into its window of efficacy. It’s just not recommended to take that chance if your ultimate goal is to prevent pregnancy.

If you’ve got the ability to plan ahead, it makes more sense to use a more reliable form of contraception. And if you’re confused about what kind is the best for you, I’ve compiled the definitive guide to birth control options that’s sure to help you decide.

What are the side effects of the morning-after pill?

As with most medications, there are sure to be side effects when using the morning-after pill. I mean, you are using to prevent ovulation and without ovulation there will be no substantial progesterone production. So, yeah, hormones will be off, but that’s not the only thing you should be prepared for.

Short-term side effects

The most commonly reported adverse side effects include:

  • Nausea
  • Vomiting
  • Abdominal pain
  • Dizziness
  • Breast tenderness
  • Headache
  • Fatigue
  • Changes to the menstrual cycle 
  • Back pain

Most women report that their side effects subside within a few days, and according to studies, regain their period within a week of the normally expected start date.

Compared to an unwanted pregnancy, these side effects are considered mild, but it is important that you evaluate what is best for you. And when in doubt, have a chat with your doctor or pharmacist who dispenses emergency contraceptives.  

Possible long-term side effects

There have been multiple anecdotal reports of ectopic pregnancy occurring after emergency contraception use. Unfortunately, there’s just not enough data available to support a firm correlation.  

Likewise — some studies suggest a correlation between LNG use and breast cancer. While we certainly don’t have enough data to draw conclusions, and the drug is only in your body for a short time when used for emergencies — it’s just something to be aware of. 

And if you’re relying on Plan B contraception for more than the occasional “whoops” then please check out our contraception guide so you don't have to stress.

If you experience severe abdominal pain or bleeding or spotting that lasts more than a few days in the 3-5 weeks after taking the morning-after pill, contact your healthcare provider to get everything checked out.

Can the morning-after pill cause hormone imbalance?

Because the morning after pill works by suppressing ovulation, it can temporarily result in symptoms of hormone imbalance. You see, for women to make sufficient progesterone we need to ovulate.

Following ovulation there is a structure called the corpus luteum that then secretes progesterone to carry us through the luteal phase. Without ovulation the corpus luteum doesn't form and progesterone production isn't sufficient.

Symptoms of Low Progesterone:

  • Fibrocystic breasts
  • Mid-cycle spotting
  • Anxiety
  • Insomnia
  • Irritability
  • Menstrual cramps
  • Heavy or irregular menses
  • Short cycles

Remember, blocking ovulation is how this medication can prevent pregnant, so it is a trade off. The symptoms of low progesterone should resolve within a cycle or two. If it doesn't, contact your doctor.

You can support your body in finding balance again by using my free hormone balancing meal plan and recipes, as well as reading up on how to balance hormones naturally.

Who should not use emergency contraception?

According to the World Health Organization, there are no medical contraindications for the use of emergency contraception pills. 

Certain drugs, though, can and will interfere with the effectiveness of the morning-after pill. Be aware that if you are taking any of the following you should consult with your doc or pharmacist before relying on Plan B to prevent pregnancy — you may need to adjust dosage:

  • Antacids
  • Seizure medications
  • Barbiturates
  • St. John’s Wort
  • Enzyme inducers — such as Dilantin, rifampicin or griseofulvin
  • HIV/AIDS medications

Women who have BMI over 25 may also find they need to adjust their dosage. Studies suggest that doubling the dose for these women is an effective strategy. Yes, I know how flawed the BMI can be, but this provides us general screening to make general recommendations. Talk with your doctor or pharmacist about individual recommendations to meet your needs.

Which type of oral emergency contraception should I choose?

If you’re currently using another form of hormonal birth control, but you’re in need of emergency contraception because you forgot to use your regular method, be mindful of which pill you choose. LNG can be more effective in these cases than UPA because the other synthetic hormones in your regular birth control can affect how well UPA works. 

Also — if you take UPA, try not to start up a new hormonal birth control regimen immediately for the same reason. The pill, patch, shot, etc. can interfere with the efficacy of Ella®, so most experts recommend waiting for 5 days after taking it before starting a new form of birth control.

Likewise, don’t take more than one of the recommended dose…this doesn’t give you and extra protection, and may actually make the medication less effective.  

What if I’m breastfeeding?

The scientific evidence available suggests that there’s no adverse effect on the baby’s growth or development if the mother uses LNG in an intrauterine device or implant while breastfeeding. The same conclusions are drawn for oral ingestion. And the CDC reports no adverse outcomes associated with UPA use and breastfeeding.

However, it’s worth noting that the Ella® package insert discourages breastfeeding and the CDC recommends in the same report where it finds no adverse outcomes to wait 24 hours before resuming breastfeeding.

European recommendations suggest waiting 7 days before continuing to breastfeed your child.

The reality is, we don’t totally know if there are any long term issues so it is best to use caution and talk with your doctor.

What if I’m pregnant?

Some women might worry that if they take the plan B pill and they are already pregnant (but don’t realize it) they could affect the health of the pregnancy. But no birth defects or developmental issues have been reported by women who didn’t realize they were already pregnant and took the morning-after pill.

And since the morning-after pill works by preventing pregnancy, there’s no risk of a miscarriage, either.

Again, many women have been incorrectly told Plan B is used to cause abortions. This isn’t correct. Its job is to prevent pregnancy from occuring.

How often can you take Plan B?

There’s no “limit” to the number of times you can take the morning-after pill…but that doesn’t mean you should rely on it as your primary form of contraception.

If you’re sexually active — it makes much more sense to use a more reliable form of regular birth control like condoms, IUD, the pill, or the patch. See the contraception guide to get informed about your options. 

In this study, repeated use of UPA was deemed safe, but ovulation still eventually occurred. So this means you can’t rely on it as a form of regular birth control. 

Can you get pregnant after taking the morning-after pill?

The great news about emergency contraception is that it appears to have no effect on your future fertility. If you change your mind and decide to get try to get pregnant during your next ovulation, you shouldn’t have any issues from having taken plan B. 

Your cycle may be a little out of whack the month following the use of the morning-after pill, so it’s best to track signs and symptoms of fertility (basal body temperature, the texture of cervical mucus, etc.) as your fertile window may change a bit. 

Will I be terminating a pregnancy if I take emergency contraception pills?

NO. There’s a lot of misinformation out there regarding this subject. And it contributes to shame and stigma surrounding access to emergency contraception — so spread the word! 

Say it with me:

Taking the morning-after pill does not and cannot terminate a viable pregnancy.

These medications work before a pregnancy is established by delaying ovulation…which means that an egg doesn’t get released. No egg, no embryo.

Are there other emergency contraception options?

The most effective form of emergency contraception isn’t actually a pill at all — it’s having an intrauterine device (IUD) placed in the cervix.

The problem with this method is that there are several barriers to access…women have to:

  1. Find a doctor
  2. Make an appointment
  3. Likely take off work to go to the appointment
  4. Do all of this in an extremely short time frame after having had unprotected sex

It’s just not as easy as getting the pill at your local pharmacy or ordering it online, and IUD’s can be cost-prohibitive to purchase if they’re not covered under your insurance plan. 

It’s important to note that when considering your options, IUDs provide long term birth control as well, so if you decide to have one placed, you won’t have to worry about birth control for some time — in some cases up to 10 years. You can read more about hormonal IUDs and non-hormonal IUDs in the articles I've written.

Also — this study showed that the likelihood of pregnancy for women who choose to orally ingest LNG AND get an IUD placed was less than 1%. 

Where can I get the morning-after pill?

All of the options containing LNG are available over the counter, without age restriction, or a prescription from most drug stores or pharmacies in the US. 

You can even order generics on Amazon. Be careful though, even if you’re opting for overnight shipping, it may not get to you in time to actually be effective. If you’re not on a regular form of birth control, it may be a good idea to order one to have on hand in case of an emergency. And like all things Amazon, check the seller to ensure you’re getting it from a reputable source as counterfeit medications and supplements are sometimes sold here.

NURX offers both Plan B® and Ella® with online consultations and fast shipping. 

Ella® can be obtained with a prescription from your doctor, or can be ordered online through their website which offers a digital consultation and overnight shipping.

If there’s a Planned Parenthood clinic near you, they can also help you find emergency contraception options.

How do I get emergency contraception pills for free?

If you have medical insurance, be sure to use it! In some cases, insurance covers the morning-after pill and, depending on your deductibles and copays can be obtained for free or at least at a reduced cost.

Some health clinics and Planned Parenthood may also offer budget-friendly options as well, so if the price is a concern, be sure to investigate locally. 

The Morning After Pill is a Tool

No one wins if women feel scared, worried, or ashamed to seek options that help them prevent pregnancy.

Let’s help break through myths, stereotypes, and completely bad information and support each other in our journeys to find the right method of contraception. Emergency contraception is a tool we have available for when mistakes happen. We don't need to vilify it or fear it.

If you do find that you have longterm side effects, talk with your doctor. And if you find that you're using it frequently then it is a good idea to find a reliable method to prevent pregnancy ongoing.

If this article has helped you sift through the true and the false, be sure to share it! 

Also, you can grab my free meal plan + recipes to help optimize hormones, plus receive tons of valuable, educational material that’s sure to help you make informed choices regarding women’s health, sexuality and birth control!


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About The Author

Dr. Jolene Brighten

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Dr. Jolene Brighten, NMD, is a women’s hormone expert and prominent leader in women’s medicine. As a licensed naturopathic physician who is board certified in naturopathic endocrinology, she takes an integrative approach in her clinical practice. A fierce patient advocate and completely dedicated to uncovering the root cause of hormonal imbalances, Dr. Brighten empowers women worldwide to take control of their health and their hormones. She is the best selling author of Beyond the Pill and Healing Your Body Naturally After Childbirth. Dr. Brighten is an international speaker, clinical educator, medical advisor within the tech community, and considered a leading authority on women’s health. She is a member of the MindBodyGreen Collective and a faculty member for the American Academy of Anti Aging Medicine. Her work has been featured in the New York Post, Forbes, Cosmopolitan, Huffington Post, Bustle, The Guardian, Sports Illustrated, Elle, and ABC News. Read more about me here.