Plan B is Contraception

The evidence is overwhelming. Pass it on.

Plan B, a.k.a. the morning after pill, known medically as post-coital contraception or emergency contraception pills (ECPs) is in the news again. And again this is due to the inability of members of the GOP to understand basic science, or not caring about the science because lies about abortion get attention as well as votes.

The latest Republican who is completely unable to grasp the facts about Plan B is Marjorie Taylor Greene. It is not a shocker that the QAnon supporting Representative from Georgia who is the living personification of the Dunning-Kruger Effect can’t grasp basic details about Plan B. Last week, in opposition to the “Equal Access to Contraception Act for Veterans,” she claimed that “Plan B kills a baby in the womb once a woman is already pregnant.” (The Equal Access to Contraception Act for Veterans prohibits The VA system from charging any co-payment for contraception).


Never has a medication been more misunderstood than poor Plan B, which is the hormone levonorgestrel (LNG) taken after unprotected intercourse to prevent pregnancy. Despite the long-standing misconception that Plan B is an abortion pill or abortifacient, it was never marketed for this purpose and never even proposed as an abortion drug. There has never been any data suggesting it can cause abortion, and there is significant data showing it only works by inhibiting ovulation. The International Federation of Gynaecology and Obstetrics (FIGO), The American College of Obstetricians and Gynecologists (ACOG) and the World Health Organization (WHO) all say that it only works by inhibiting ovulation. Even The Catholic Health Association of the United States says it only works by inhibiting ovulation. No really, They do! Here are their words (click here for the full document):

The vast preponderance of scientific evidence on the mechanism of action of levonorgestrel, especially more recent scientific studies, suggests that it does not have an abortifacient effect, that is, it does not make the endometrium unreceptive to the implantation of an embryo. 

I mean, when you’ve lost the quarterly resource for the Catholic Health Ministry that says something. And by the way, that statement is from 2012. Even the Catholic Health Ministry has been on board with the facts for almost a decade.

It would be easy to laugh off Marjorie Taylor Greene as a crank, but she is in our government and she isn’t the only idiot swinging this bat. In fact, there are many with sharper intellects who promote the lie that Plan B is associated with abortion. Remember back to the Hobby Lobby case, where the Supreme Court said it only mattered if you believed a contraceptive was an abortifacient (meaning a drug that causes abortion) to make it an abortifacient. Here are Justice Alito’s words as a stark reminder, (Plan B was one of the four contraceptive methods):

“The owners of the businesses have religious objections to abortion, and according to their religious beliefs the four contraceptive methods at issue are abortifacients. If the owners comply with the HHS mandate, they believe they will be facilitating abortions…It is not for us to say that their religious beliefs are mistaken or insubstantial.”

If Plan B becomes an abortifacient then by extension all hormonal contraception is at risk of being falsely labeled as an abortifacient. And looking at the tide of anti abortion laws cropping up, this matters a lot. The long term goal of the Susan B. Anthony List, a forced birth group closely aligned with the GOP, is not to just get abortion banned, but to get contraception banned. Even if Roe doesn’t fall, branding Plan B as an abortion drug is just another way to keep false narratives about abortion in play. Being “tough on abortion” gets votes in many districts.

Stopping people like Marjorie Taylor Greene from spewing lies about abortion isn’t possible. However, what you can do is to arm yourself with facts and to pass good information along proactively. We can’t play defense here, meaning we can’t be waiting for lies about Plan B and then respond. Playing catch up after the lie is less effective than being the first to the message. What we need to do is regularly share information about Plan B being a contraceptive that works by inhibiting ovulation.

So here’s what you need to know to do just that.

Why Do People Think Plan B Causes Abortion?

Some people erroneously think Plan B was always an abortion pill, but that isn’t true. Mifepristone is the pill used for a medication abortion. They were both approved around the same time, Plan B in 1999 and mifepristone, or RU-486 as it was also known, in 2000. As they were both in the press a lot in the 1990s it is easy to see how they might be confused with each other. Mifepristone is an anti progesterone, that is why is causes abortions as progesterone is needed to maintain a pregnancy. Plan B is levonorgestrel, which is an progestin, meaning a drug that acts like progesterone. So right there you have a big hint that Plan B can’t cause abortions as it has the opposite effect of the drug we know causes abortions.

Others mistakenly think that Plan B can prevent implantation of a blastocyst (fertilized egg). This false belief likely happened because when post coital contraception was first introduced the method of action was unknown. Fun fact, the first clinical trial for post coital contraception was published in 1974 by Dr. Albert Yuzpe, who was my mentor in residency. The Yuzpe method, as it is often called, involved high doses of ethinyl estradiol (an estrogen) and dl-norgestrel (a progestin, or progesterone-like hormone very similar to the one in Plan B today). Yuzpe’s original study involved biopsies from the lining of the uterus showing this dose of progestin affected the lining, although whether this effect could actually impact implantation wasn’t known. These results likely led to the hypothesis that one method of action could be prevention of implantation of a fertilized ovum. It is also important to remember that when the Yuzpe method was being studied the ultrasound technology that we have today did not exist.

With further research it became clear the estrogen could be dropped. This was beneficial as the estrogen caused a lot of the side effects and theoretically could be riskier for women over 35 who smoked or had cardiovascular disease. The best option was levonorgestrel (a progestin) by itself, which was FDA approved in 1999. When Plan B was studied in the 1990s the mechanism of action was believed to be inhibiting ovulation, but there wasn’t the data to say for certain. That is why the package insert for Plan B which was written in 1999 says the following:

“Plan B One-Step is believed to act as an emergency contraceptive principally by preventing ovulation or fertilization (by altering tubal transport of sperm and/or ova). In addition, it may inhibit implantation (by altering the endometrium).”

And that is also why this wording is also on the FDA site. 

“If fertilization does occur, Plan B may prevent a fertilized egg from attaching to the womb (implantation). If a fertilized egg is implanted prior to taking Plan B, Plan B will not work.”

These two statements are often held up as proof Plan B affects implantation, and hence causes abortion. What is often lost in the discussion is that package inserts and FDA labeling are mostly legal documents, not medical ones. There was never any study showing that Plan B affects implantation. And we now have excellent data proving how Plan B works and that is doesn’t cause abortion, even using the criteria of preventing implantation.

The Science is Clear, Plan B inhibits Ovulation. 

Meaning Plan B has earned the name post-coital contraception. It’s literally a birth control pill that you take after sex.

First of all, if progestins affected implantation we’d know by now because they are in every method of hormonal contraception. But the way we really know is the performance of the progestin-only pill, which contains a progestin, similar to the one in Plan B, but no estrogen. It has a higher failure rate than birth control pills with estrogen. This is because it only stops ovulation about 50% of the time. It’s other method of preventing pregnancy is by affecting cervical mucus, so sperm can’t swim through to the uterus. But the progestin is cleared very rapidly from the body, so it needs to be taken at the same time every day or levels fall to low. If progestins affected implantation, the failure rate of this pill wouldn’t be higher than the regular birth control pill with estrogen as many of those contain the exact same progestin as the progestin-only pill.

Also, how does a pill that has a progestin (Plan B) cause an abortion, when a progestin has exactly the opposite effect of the abortion pill (mifepristone)?

But I digress. We don’t want logic, we want studies, and here they are: 

Animal studies: There are two, one using rats (read it here) and the other with monkeys showing no effect of Plan B on implantation or other post fertilization effects. Plan B was only effective when it was given before ovulation. 

In vitro studies: Meaning in the lab. These studies expose cells from the lining of the uterus (the endometrium) to levonorgestrel (the hormone in Plan B) looking for any kind of signaling changes that might suggest a negative effect on implantation. There is this study that looked at markers of receptivity for implantation. No effect. And this study, that shows levonorgestrel does not prevent the blastocyst (fertilized egg) from attaching to the endometrium. No study has shown any concern with Plan B and implantation.

Human studies: Multiple studies have looked at Plan B showing it affects ovulation when given at the right time in the cycle. These studies are very intricate, following hormone levels as well as the size of the developing follicle (sac in the ovary that contains the egg) on ultrasound. Then there is this study (click here to read), which is perhaps the most elegant of all., Researchers followed 87 women who took Plan B  during the 5 days before ovulation, and 35 who took it on the day of ovulation. Looking at standard pregnancy rates, of the 87 who took it before ovulation 13 should have become pregnant, but Plan B prevented all of these pregnancies. Of the 35 women who took Plan B on the day of ovulation, 7 should have become pregnant and 6 did (so within the margin of error for an expected pregnancy rate). If Plan B affected both implantation and ovulation the pregnancy rate for those who took it on the day of ovulation should have been lower.

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So Why with ALL this Data Can’t We Change the Plan B Narrative to One that is Factual?

I suspect there are three reasons. 

  1. Plan B is still confused with the medical abortion pill (as previously discussed).

  2. The illusory truth effect, meaning we all mistake repetition for accuracy. There is a reason the Republicans keep repeating the lie. They want it to stick. When you spread the truth about Plan B, don't repeat the lie. It’s better to say “Plan B prevents ovulation, this is how it works. There are many studies showing this is the only way it works.” Instead of saying, “Plan B isn’t an abortifacient.” We have to stop headlines that reinforce the false connection between Plan B and abortion.’

  3. People find it hard to believe that a medication we recommend people take at any point in the menstrual cycle, only affects one point of the cycle - ovulation. However, the reason we recommend taking Plan B regardless of where a person is in their menstrual cycle isn’t because we think it has other effects, such as affecting implantation, it is because of the unpredictable timing of ovulation. Let’s be real, most of us aren’t walking around with the blood work and ultrasound findings to tell us if we are in the optimal pre-ovulation Plan B window. In addition, sperm lives for several days in the uterus. Basically the permutations and combinations of when you are actually at risk for conceiving are almost impossible to work out after the fact (especially at 2 a.m.), so it is really just better to use Plan B (or a different form of post coital contraception) if you have unprotected intercourse regardless of the day of the month. 

So let me tell it to you straight and please spread the word…

  • Plan B was never an abortion pill.

  • There is no credible study that shows Plan B can affect implantation.

  • Multiple studies show Plan B prevents ovulation and that this is the only method of action.

  • And in the words of the The Catholic Health Association of The United States, “…current language regarding implantation should not be included in LNG ECP labeling.” Meaning, the Plan B product label should be changed to reflect the fact that it doesn’t affect implantation.

Plan B is contraception. And if all this science isn’t proof enough, then nothing will be. So this is a fight that we absolutely must win. Be proactive and spread the word.