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abortion, Contraception, evidence based medicine, war on women

How does Plan B really work? Don’t ask the Supreme Court, ask an OB/GYN

Never has a medication been more misunderstood than poor Plan B (levonorgestrel or LNG), a post coital contraceptive (a.k.a. morning-after pill).

It’s not just Justices Alito, Thomas, Roberts, Scalia, Kennedy and Dr. Hobby Lobby who fail to grasp the mechanism of action, but many other people are confused including journalists (the NY Times has an error in the mechanisms of action in a recent article) and even some doctors. The misinformation about LNG post coital contraception has essentially become urban medical myth, sometimes perpetuated with good intentions (reporters trying to strive for due diligence or health care professionals trying to teach students or explain to patients) and sometimes with bad intentions (Justice Alito et al and the American Association of Pro-Life OB/GYNs I’m looking at you).

Fortunately there are excellent studies that tell us exactly how Plan B works so let’s get to it:

Plan B is levonorgestrel, a progestin (a synthetic version of the hormone progesterone). The hormone progesterone is released by the sac that stays behind after ovulation (called the corpus luteum). The job of progesterone is to get the uterus primed to accept a fertilized egg and if implantation happens it maintains the pregnancy until the placenta can produce its own progesterone. This hormone is pro-gestational, hence the choice of the name pro-gesterone. This is a bit of a spoiler alert because a synthetic version of a pro-gestational hormone is unlikely to do the exact opposite.

How does plan B work? It has one and only one mechanism of action, it inhibits ovulation.

A variety of hormonal changes happen as the ovary readies an egg (a.k.a follicle) for ovulation. Ovulation, the actual release of the egg, is triggered by a massive surge of a hormone called luteinizing hormone (LH). After ovulation the egg has a 24 hour window to be fertilized (it has a pretty short shelf life). Plan B when given 2 to 3 days BEFORE the LH surge can inhibit,delay, or blunt the LH surge and prevent ovulation. Outside of that 48 hours window Plan B is very ineffective.

LH_surge1

The dose of levonorgestrel in Plan B is not enough to affect cervical mucous and since it is given AFTER sex that’s a moot point. By the time you have taken Plan B the sperm has already passed the cervix and within minutes it’s in the fallopian tube. Waiting.

The single dose of levonorgestrel in Plan B is not enough to damage sperm. this has also been well-studied.  (FYI sperm can live for 5-6 days in the upper reproductive tract), so we can cross damaging sperm off the how-does-Plan-B-work list.

The single dose of levonorgestrel in Plan B is also not enough to do  anything to uterine lining and animal studies tell us that embryos exposed to the Plan B dose of LNG develop just fine and there is no impact on implantation. So even if you use the Justice Alito/Dr. Hobby Lobby version of abortion (i.e. affecting a fertilized egg) there is no possible impact. At all. This is what we call scientific fact, it is not open to interpretation. 

Hold on you say. It only works before ovulation? Why would I take it then if I weren’t about to ovulate? Well…

  • Ovulation can be unpredictable. many women have irregular cycles and even those with cycles like clock work can pop an egg out early every now and then
  • Sperm lives for 5-6 days, so even of you have sex on day 7 or 8 of your cycle (i.e. days when you are not normally fertile) the sperm might actually be there when you are fertile 4-6 days later.
  • Plan B has no contraindications and very few, if any, side effects

Basically the permutations and combinations of when you are actually fertile are almost impossible to work out (especially at 2 a.m. when the condom broke), so it is really just better to use it if you have unprotected intercourse regardless of the day of the month. That is how it was studied. However, ella (ulipristal) is more effective as a post coital contraceptive and a Copper IUD is the most effective, although both require a prescription and are significantly more expensive than generic Plan B. If you absolutely do not want to get pregnant ella or a post-coital copper IUD are better choices, but just less practical.

Just as we know that condoms work by mechanically preventing sperm from getting into the uterus, we know that Plan B works by inhibiting ovulation. To say otherwise isn’t a belief, it’s a lie.

 

 

 

Note: someone asked why does Plan B labeling indicate that it might affect implantation when I say that it does not? I felt my reply important enough to add that to the body of the post in case someone else has the same question.

Package inserts are notorious for being a “cover you legal ass and assets” rather than a reflection of state of the art science. This is because they are legal documents not medical ones, the FDA has very specific requirements as to what can and can not be put into a package insert based in the studies presented to the FDA at the time of application, and they are often outdated due to the science that has been produced since the original application.

The Plan B package insert was approved in 2006 and since that time there have been at least three studies evaluating endometrial receptivity that disprove an implantation disruption hypothesis (Palomino in 2010 Fertility Sterility, Meng 2010 Human Reproduction and Vargas 2012 Journal of Molecular Endocrinology). There was a 2001 study that indicated no impact on endometrial receptivity (Durand Contraception), however whether that one study was considered sufficient at the time of FDA submission or was even submitted I don’t know.

Our understanding of how mechanisms of action of medications evolves as new technology develops. in addition, once products become available many researchers become interested in further study. The company who makes the product is typically not invested in this specific kind of post market research as it brings them nothing financially. To get a package insert changed on new data requires a significant amount of paper work with the FDA and is very expensive. Once a product is generic (such as Plan B) there is zero motivation to make the correction.

Relying on a package insert which contains by nature a myriad of biases from 2006 and thus based on data from pre-2005 to be scientifically accurate in 2014 (especially given the robust studies published in peer reviewed journals since) is ludicrous.

In addition, the 2008 FIGO statement on LNG post coital contraception says a “review of the evidence suggests that LNG ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in LNG ECP product labeling.”

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Discussion

40 thoughts on “How does Plan B really work? Don’t ask the Supreme Court, ask an OB/GYN

  1. Thank you for this post!

    Posted by Victo Dolore | July 4, 2014, 10:29 am
  2. There you go again! Using Science and Facts!

    Posted by rekster | July 4, 2014, 11:34 am
  3. That you for putting the information out there.
    Leslie

    Posted by swo8 | July 4, 2014, 12:31 pm
  4. The root of the dispute is, among other points is the following quote from the Plan B package insert which you no doubt dispute. – “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).” This suggests a possible post-fertilization effect which is the root of HL’s objection.

    Likewise, does your post support the HL contention that IUDs may have a post fertilization effect (by your point that IUDs are more effective EC) in that the post-coital placement of an IUD would not seem to effect sperm that is surely in the upper reproductive tract but (seemingly) create a uterine environment against implantation?

    Posted by Daniel Kane | July 4, 2014, 1:58 pm
    • Package inserts are notorious for being a “cover you legal ass and assets” rather than a reflection of state of the art science. This is because they are legal documents not medical ones, the FDA has very specific requirements as to what can and can not be put into a package insert based in the studies presented to the FDA at the time of application, and they are often outdated due to the science that has been produced since the original application.

      The Plan B package insert was approved in 2006 and since that time there have been at least three studies evaluating endometrial receptivity that disprove an implantation disruption hypothesis (Palomino in 2010 Fertility Sterility, Meng 2010 Human Reproduction and Vargas 2012 Journal of Molecular Endocrinology). There was a 2001 study that indicated no impact on endometrial receptivity (Durand Contraception), however whether that one study was considered sufficient at the time of FDA submission or was even submitted I don’t know.

      Our understanding of how mechanisms of action of medications evolves as new technology develops. in addition, once products become available many researchers become interested in further study. The company who makes the product is typically not invested in this specific kind of post market research as it brings them nothing financially. To get a package insert changed on new data requires a significant amount of paper work with the FDA and is very expensive. Once a product is generic (such as Plan B) there is zero motivation to make the correction.

      Relying on a package insert which contains by nature a myriad of biases from 2006 and thus based on data from pre-2005 to be scientifically accurate in 2014 (especially given the robust studies published in peer reviewed journals since) is ludicrous.

      This post is about Plan B, not the IUD. I have a post that I wrote for the New Republic that contains info on the IUD, check their website out on Monday.

      Posted by Dr. Jen Gunter | July 4, 2014, 2:40 pm
  5. Thank you for your sensible TRUE post! I’m sick of the opinions of those who know nothing yet think their opinion is scientific fact.

    Posted by Erin Bliss | July 4, 2014, 8:08 pm
  6. While I agree with everything in this article the entire scope misses the point! The federal government has no authority to tell a privately owned or any company what kind of insurance to offer including no insurance which will be the results of most of this mess
    I also as an individual can choose to work for that company or choose one that offers what I want. Individual responsibility is exactly that, individual responsibility Even long before all of this existed and as a poor starving student I could choose to buy condoms or a nicer dinner date. Making the wrong choice on my end could have had dire life changing results but I did know the federal government was not reonsible for me or my results in life
    Stop the insanity

    Posted by RedraiderRio | July 5, 2014, 9:19 am
    • So, I guess you are against the Federal government regulating business in any way? You are against any employment regulations? You are ok with having no workplace safety regulations? You are ok with no working condition regulations? You are ok with no privacy regulations that businesses are required to follow?

      Or are you just against anything the Federal government requires? Just trying to figure that out.

      Posted by rekster | July 5, 2014, 11:54 am
      • When health care is politicized as it is now, few are happy. There is a legitimate discussion to be had – should the government specify what is in health insurance? Should the employer? Should the employer just shut up and pay? The next regime in D.C. may not be so inclined to provide contraceptives in favor of something else (to please another party – because in case anyone has missed it – including me; this is not about science, it is about control). So, today if it seems like one’s boss and one’s government is in the bed room and exam room you could be correct. It is only the case because the citizenry via Congress invited them in.

        At the moment, everyone is simply vetting the level of intrusion and level of interference for the employer and the feds. This will go on for about 10 years.

        If one depends on the feds for goods and services, one can expect them to seek their own science for their own reasons. Dr. G pretty fairly laid out Plan B’s actions and answered a pertinent objection on the package insert. But the Court does not need Dr. G or her science. A million Ob-Gyns may properly agree with her but if five judges do not, that is the market we desired and created when we federalized the insurance business. Consumers of health care – and we are all consumers – become recipients with no opinion or option.

        Posted by Daniel Kane | July 5, 2014, 6:07 pm
  7. Dr. Hobby Lobby! I’m going to start using that one. Many of my patients (I’m a midwife working as a women’s health NP), unfortunately, either don’t know much about emergency contraception, or believe that it causes an abortion, due to all the awful non-scientific stuff that’s out there. Thanks for the post!

    Posted by michelleefarber | July 5, 2014, 10:10 am
  8. An article titled “The Science Behind the Birth Control in the Hobby Lobby Case” was written in which the author Jen Gunter stated that Plan B does not stop implantation of a fertilized egg. She stated regarding stopping implantation of a fertilized egg. “Plan B, which is one form of the morning-after pill, clearly wouldn’t. It works by inhibiting ovulation when given during a specific 48 hour window of the cycle. It has no other method of action. This is undisputed scientific fact. (Plan B is one of the best studied of all the methods of contraception).”

    She said this is an undisputed scientific fact??? When this is a completely false statement. Plan B’s official website states that it DOES prevent implantation. Here is an excerpt from the official website.

    “How does Plan B One-Step® work?

    Plan B One-Step® is one tablet with levonorgestrel, a hormone that has been used in many birth control pills for several decades. Plan B One-Step® contains a higher dose of levonorgestrel than birth control pills, but works in a similar way to prevent pregnancy. It works mainly by stopping the release of an egg from the ovary. It is possible that Plan B One-Step® may also work by preventing fertilization of an egg (the uniting of sperm with the egg) or by preventing attachment (implantation) to the uterus (womb).”

    This is from the Plan B One-Step Website. http://www.planbonestep.com/faqs.aspx

    This needs to be reprinted and fixed. This is an attack on religious conservatives and makes Hobby Lobby and all those who have religious concerns about birth control look to be liars. I normally never would get involved but when I see a blatant LIE written on an article from a doctor who is claiming something that is not true… it needs to be fixed. I will be pursuing this with a passion until it is.

    Posted by Georgia Grace | July 8, 2014, 10:36 am
    • So you didn’t read the article or didn’t understand it? If you did you would have seen the paragraphs at the end that explain the package insert is incorrect and why FIGO recommends changing the package.

      Posted by Dr. Jen Gunter | July 8, 2014, 11:13 am
      • I read the article and I still disagree with you and so do many other modern gynecologists. It is still possible to take the plan B after ovulation or the day of and therefore fertilization would have already occurred.

        How do you explain why OBGYN have patients who come into their office who have severe bleeding after taking Plan B and they do a test of hormone levels that show that there was pregnancy hormones present in the test and the Plan B caused an early abortion. Stated from an OBGYN! The office stated that this is something that happens with Plan B. So other doctors have stated the opposite of what you are so boldly and confidently. This is a common situation for many women. That is a scientific fact!

        Posted by Georgia Grace | July 8, 2014, 11:47 am
      • There are no studies supporting your assertion of Plan B resulting in “a test of hormone levels that show there was pregnancy hormones present.” Please find a peer reviewed study that supports that claim otherwise go elsewhere with your venom. Also, the irregular bleeding than can happen after Plan B is due to the effect of levonorgestrel on ovulation.

        As Plan B is not 100% effective some women will get pregnant (about 5% a month with no birth control and 2% with Plan B). As there is normally a high degree of early pregnancy loss naturally (i.e. miscarriage) some of the Plan B failures will miscarry. That’s not a Plan B effect.

        Your claims are hearsay and your conclusions are based in a poor understanding of reproductive biology and the scientific method.

        Posted by Dr. Jen Gunter | July 8, 2014, 12:33 pm
      • Also, you can say whatever you want about FIGO recommending to change the package in 2008 but the scientific fact is they have NOT changed the package. To this day in July 8th, 2014, the statement that it may prevent implantation is still on the plan B packaging and website. It’s there for a reason!!! If what you state was true, it would be changed but it’s NOT!

        Posted by Georgia Grace | July 8, 2014, 12:03 pm
      • Again, clearly you did not understand or read the post. No manufacturer ever invests $ in changing the package insert after a product goes generic.

        Posted by Dr. Jen Gunter | July 8, 2014, 12:35 pm
      • Not hearsay but personal experience. Not venom just truth.

        Posted by Georgia Grace | July 8, 2014, 1:36 pm
      • If your comments are based on your personal experience taking Plan B it still does not support your claim that the medication interferes with implantation. If a doctor told you that, they were wrong. If you had irregular bleeding or an early or late period after Plan B that is a well known side effect and does not imply a post fertilization impact. The package insert was not updated for all the reasons described above. Personal experience does not support the erroneous claims that Plan B is an abortifacient.

        Posted by Dr. Jen Gunter | July 9, 2014, 10:04 am
      • What’s wrong with the other 16 birth control methods Hobby Lobby does approve of?

        Posted by Mark Conte | July 9, 2014, 12:22 pm
  9. ^The ruling allows companies to now refuse coverage of ANY type of contraception, so those 16 aren’t givens anymore. The wording of the ruling also apparently states companies don’t have to cover “counseling” on methods they do not approve. So, what? They’re just not going to cover pap smears if your GYN drops the “IUD” bomb during the visit? Unclear how that’s going to work under HIPAA.
    Also, the four methods that were originally in dispute are coincidentally the most effective and the most expensive. Some women can’t use hormonal methods at all, so the copper IUD is the best option ($1,000??? Pocket change, of course). Women unhappy with their method tend to use it sporadically, hence unintended pregnancies happen if women are “on” the pill. Unintended pregnancies tend to cause a woman to seek abortion, or have an unhealthy pregnancy. Also, I’ve seen IUDs used in lieu of oral contraceptives if a patient’s parent or partner is performing what we call reproductive coercion…throwing pills away, refusing to use condoms, trying to impregnate someone against their will, etc. Those women benefit from a discreet, reliable method like the IUD, because they may not be a position to simply “abstain” from sex without partner retaliation (and if anyone answers “She should just leave him!”, you know very little about patterns of intimate partner violence on a broad scale, even if you have your own experiences).
    So no, there’s nothing wrong with the “other 16″; they’re just a viable option for every woman.

    Posted by LT | July 12, 2014, 7:36 am
  10. *not a viable option.

    Posted by LT | July 12, 2014, 7:37 am
    • The Supreme court has ruled. Unless you want to change our system of government, Get over it. You can buy any drug you want at the local Walmart.

      Posted by Mark Conte | July 12, 2014, 8:13 am
      • The Supreme Court also reverses their rulings…Dred Scott being the most obvious example. Get a couple of non-corporate judges on SCOTUS and this ruling will be toast.

        Posted by redheadedfemme | July 14, 2014, 6:42 am
      • This is not quite Dred Scott. In fact, it is the exact opposite for the fetus. Now go run out and save a puppy because you love animals.

        Posted by Mark Conte | July 14, 2014, 8:53 am
      • I don’t know what saving puppies (in my case it would be kittens) has to do with what we’re talking about. My point was that the Supreme Court does reverse their rulings. I think this ruling is just as wrong as Dred Scott’s was…therefore, get some different, non-partisan (or, more, accurately, non-Catholic, since Alito and Scalia obviously let their religiosity overwhelm their legalese) judges on the bench, and it will probably be reversed.

        Posted by redheadedfemme | July 14, 2014, 10:35 am
      • You’ll drive 35 miles to save some kittens trapped in a locked car but will flush your own flesh and blood down the toilet with the disdain you have for a cockroach. Get it now> Religion has nothing to do with it. The last time I went to church was when my friend got married 8 years ago. It’s a human rights issue, like the slavery issue and the gassing of the Jews and for the current world, the bombing of innocent women and children in Palestine which the whole world is turning a blind eye to. Going to a PETA Meeting tonight?

        Posted by Mark Conte | July 14, 2014, 3:55 pm
      • Boy, those goalposts are just tumbling down the mountainside, aren’t they?

        Obviously you have no answer to the fact that the Hobby Lobby ruling is just plain wrong and there’s a good chance a future Supreme Court will reverse it. I never mentioned abortion, so why are you dragging that in? Also, what the hell doesn PETA have to do with anything? Really, Mr. Conte, you’re just frothing at the mouth. As you so snidely told me, “Get over it.”

        Posted by redheadedfemme | July 14, 2014, 4:02 pm
      • It’s just plain wrong in your eyes. However majority rules in this country. Case closed.

        Posted by Mark Conte | July 14, 2014, 6:59 pm
      • Not necessarily. As I said, get one or two new justices, and who knows?

        http://money.howstuffworks.com/10-overturned-supreme-court-cases.htm

        Also, the Senate will hold a vote on legislation to reverse the decision.

        http://www.politicususa.com/2014/07/14/senate-vote-bill-reverse-hobby-lobby-decision.html

        So I wouldn’t be too sure of that.

        Also, the “majority” doesn’t rule if the majority rule is unconstitutional. See “same-sex marriage bans overturned.”

        Posted by redheadedfemme | July 14, 2014, 7:10 pm
      • Let’s cut all the bs. You want the insurance company to pay for the more expensive birth control. The Supreme Court said you have to pay for your own. That’s it. If as you say this ruling can be reversed, so can other laws like Roe vs Wade. Think about that.

        Posted by Mark Conte | July 14, 2014, 8:34 pm
      • Well, obviously. But can you really imagine the one or two justices who would be needed to reverse this ruling…then turning around and reversing Roe v. Wade? Think about that, dude. Not hardly.

        You didn’t even read the article, did you? Cost has nothing to do with it. The five Catholics wrote their opinion on the bullshit idea that a false belief trumps scientific fact.

        Also, since my other comment is still in moderation, you said: “However majority rules in this country. Case closed.”

        The “majority” doesn’t rule if the rule is unconstitutional. See “same-sex marriage bans overturned.”

        Posted by redheadedfemme | July 14, 2014, 9:14 pm
  11. I read and understood the explanation. I took the plan b about cycle day 18th and I had my period about a day or two later. I didn’t chart my cycles like I do now and I now know that I ovulate between cycle day 18 and 22 if ovulation isn’t delay by stress or whatever and I mentruate about about 14 to 15 days later which ranges my cycles 33,34,35 or 36 days long. So how come I menstruated about two weeks and a few days after my previous menstration when I took plan b? I had never gotten a period that earlier in my whole menstruating years, infact, that’s the only time I’ve ever! And now that I understand my menstrual cycles better, I have come to conclude that indeed plan b interferes with implatation as I may have taken it on the day or the day after I ovulated. If you have an explanation for that, it would be most appreciated. Thank you.

    Posted by Mrs.Prongs | August 17, 2014, 8:15 am
    • Bleeding does not imply a normal menses. The hormones in plan b can indeed cause irregular bleeding

      Posted by Dr. Jen Gunter | August 17, 2014, 9:30 am
      • Thank you so much for taking the time to answer by question. I thought about that too but I wasn’t sure as that particular period was just as long and as heavy as my regular periods of 7 days (first four are heavy and last day or two is/are spotting). Don’t know if that changes anything.

        Posted by Mrs.Prongs | August 17, 2014, 10:51 am
    • This happened to me,I took plan b, I had my period about 5 days later (9 days earlier than normal) then the next month skipped a period completely, then the following month back on track…i Just thought I would share as it really freaked me out skipping my period…i went to like3 doctors all who said it could happen and still didn’t believe them to my period came back.

      Posted by Sarah | August 28, 2014, 1:28 pm

Trackbacks/Pingbacks

  1. Pingback: How Does Plan B Really Work? Don’t Ask The Supreme Court, Ask An | Edmund's Page - July 5, 2014

  2. Pingback: The Hobby Lobby Decision | Unsolicited Feedback - July 16, 2014

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  4. Pingback: Hobby Lobby and Gender Discrimination: Refocusing the Conversation | Birth Anarchy - October 13, 2014

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