Friday, February 24, 2006

Guest blogger: Dr. David Toub, M.D.

emergency contraception is not an abortifacient

I'm so tired of this issue...

Last week, the TV show Boston Legal aired an episode in which a victim of sexual assault was denied emergency contraception (EC) because she was evaluated in a Catholic hospital. The Clara Bell Duvall Reproductive Freedom Project of ACLU-PA and other organizations encouraged people to host events to accompany the broadcast, and a good deal of attention was generated about EC.

So of course, on the Web, there have been a host of comments about the broadcast, many of which refer to EC as an abortifacient, something that causes an abortion. A Catholic Web site even posted something by the head of the Catholic League, accusing all of us on the Philadelphia ACLU board of being "anti-Catholic." Of course, I chimed in and tried to correct some misconceptions (bad pun) about EC and its provision to women who are victims of sexual assault. Many of the posts on ABC's Boston Legal forum simply represented a lack of knowledge about EC, not a right-wing philosophy, and when I pointed out what EC is and does, and that it is not an abortifacient, people seemed to appreciate the information. Not so with the Catholic site, and I'm also curious if the right-wing Jewish World Review publishes my rebuttal to an article about the Boston Legal episode and EC that was anything but accurate.

So what really is the truth about EC? It's pretty simple---emergency contraception prevents a pregnancy from occurring after unprotected intercourse. It is up to 89% effective in preventing undesired pregnancy when used within 72 hours of unprotected intercourse. While it may still prevent some pregnancies after 72 hours, It is much less effective (one exception: the IUD can work as an effective emergency contraceptive even five days after unprotected intercourse).

EC has no effect on an ongoing pregnancy. It is not teratogenic and does not disrupt an implanted embryo. While some believe that life begins at conception, this is a religious concept, not a medical one. Pregnancy results from an implanted embryo; one is not pregnant during the 5-7 days it takes for a fertilized oocyte to transit down the fallopian tube into the uterus. Indeed, as Charles Lockwood points out, for the first two weeks after conception, part of the blastocyst is multipotential, with cells that could develop on their own into an embryo, so there is nothing that particularly makes it a unique "person" at that point. And that is at least a week after implantation, so at 72 hours post-conception, one cannot argue that this represents life as we know it.

So how does EC work? While the precise mechanism of action remains to be conclusively delineated and proven, there is very good experimental and clinical evidence that EC primarily works by inhibiting ovulation and preventing fertilization through various means (inhibited sperm transport, etc). There is no good data supporting the idea that EC functions by preventing implantation of a fertilized oocyte. A review by Croxatto and colleagues concluded that:

"Studies searching for possible alterations of the endometrium at the time implantation would normally take place, found minimal changes of doubtful significance. Recent studies in animals cast serious doubts that LNG prevents pregnancy by interfering with post-fertilization events."

They also point out, very astutely, that EC does have a non-trivial failure rate, and this is likely to be due to treatment provided too late to prevent pregnancy. Were EC to prevent implantation, which can occur a week or more post-ovulation, it is unlikely that administering EC after 72 hours from unprotected intercourse would be associated with a significant failure rate.

So it is extremely unlikely that EC prevents implantation to any material extent, and its action is contraceptive (preventing conception) rather than interceptive (preventing pregnancy after conception has occurred). Pregnancy results from the successful and sustainable implantation of a fertilized oocyte into the endometrium. EC has no effect on an implanted oocyte, and is not an abortifacient. Arguments to the contrary are faith-based, not medical or scientific in nature.

James Trussell and the Office of Population Research at Princeton University have an excellent site with evidence-based information that also substantiates the concept that EC does not work by preventing implantation.

The truth is that EC can prevent a significant number of abortions. This is a goal that people from both sides of the abortion divide should be able to embrace and use as a starting point to find common ground.

Dr. David Toub is a member of the board of directors of the Philadelphia chapter of ACLU-PA. Check out his blog, david's waste of bandwidth.

3 Comments:

Blogger Chrissy said...

Wait, so, what I was told in school and by planned parenthood that EC makes the uterine walls in hospitable to the embryo is b.s.? Why are we being told that by pro-family planning organizations/people? Is it that it's just easier to explain it that way?

Also, with your explaination would EC make etopic pregnancies more likely?

I guess, I'm more confused than I was to start off with.

10:19 AM  
Blogger David Toub said...

Wait, so, what I was told in school and by planned parenthood that EC makes the uterine walls in hospitable to the embryo is b.s.? Why are we being told that by pro-family planning organizations/people? Is it that it's just easier to explain it that way?

Also, with your explaination would EC make etopic pregnancies more likely?

Chrissy, your confusion is understandable, and common. I was taught the same thing years ago, but fortunately the science has progressed over the years so we understand at least some things about EC in greater detail.

We know that the hormones in EC (and in oral contraceptive pills in general) do have effects on the uterine lining. However, it has never been shown in any reproducible fashion that the changes produced by EC are a mechanism by which EC prevents pregnancy. There have been many studies that indicate that EC works almost exclusively, if not entirely exclusively, by interfering with ovulation and also by impairing fertilization (should ovulation have occurred).

If my memory serves me, there was a study many years ago in which researchers placed women on either EC or a fake pill, and collected menstrual blood from them. In many cases, women will have a slightly late period, and that can be due to spontaneous loss of a very early embryo that just was not meant to be. If EC worked in part by impairing implantation, then the women on EC should show some evidence for early embryos in their menstrual blood. The study showed some early pregnancy loss among the women who were not taking any contraception, and none of the women on EC had any evidence of pregnancy loss. Thus, it seems very unlikely that EC prevents implantation.

If EC prevents pregnancies by either preventing ovulation or preventing fertilization, there would be no increased risk of ectopic pregnancies, either. And that is in fact what we see. Note that this is notthe case with mifepristone (RU-486), which does terminate established intrauterine pregnancies but is not at all effective in preventing ectopic pregnancies. Interestingly, the drug that many of us used to use for medical abortion, methotrexate, is also useful in terminating ectopic pregnancies.

Again, EC does not cause an abortion, unlike methotrexate or mifepristone. It is nothing more than a higher dosage of conventional birth control pills.

2:49 PM  
Blogger Airin Ahmed said...



Wow, Nice Post, I like It………….
Best of Luck………..

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5:17 AM  

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