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Context and Variation


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Here is Some Legitimate Science on Pregnancy and Rape

The views expressed are those of the author and are not necessarily those of Scientific American.


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Trigger warning: discussion of violence against women and graphic mention of miscarriage.

 

So Congressperson Todd Akin of Missouri has said some interesting things. Referring to the possibility of pregnancy after rape, and whether abortion should be allowed in this circumstance, he said according to his understanding “if it’s a legitimate rape, the female body has ways to try to shut that whole thing down,” but that, should one embryo slip through, that “the punishment should be on the rapist, and not attacking the child.” In Akin’s non-apology about his insensitivity towards the “thousands” of rape survivors each year, he remains firm on the point that abortion shouldn’t be allowable for pregnant victims, saying “…I believe deeply in the protection of all life and I do not believe that harming another innocent victim is the right course of action.”

I don’t like writing about rape. I didn’t like turning my Laser Beam Eyes of Ladybusiness Justice on my Twitter feed today, which was a constant stream of information, reaction to, and anger about Akin and his baseless, stupid comments. Rape reminds me of the ways in which I am powerless, simply by being female. It doesn’t matter how many contact sports I play or muscles I build. It doesn’t matter how big my husband is. Sometimes I look at my life, and see what I’ve built, and how I’ve tried to protect myself. And I wonder what measures other women have taken for the same reasons, measures that ultimately mean little in the face of cultural conditioning to make men happy, of sexual dimorphism in musculature, of a powerful rape culture.

Some legitimate context

Unfortunately, it is rather normal to be a survivor of sexual assault if you are female. One out of six women in the United States have been the victim of rape or attempted rape, and that is using a rather tight definition that does not include many kinds of assault victims can experience. 64,080 women were raped in the US between 2004-2005. Sixty four thousand and eighty. That’s tens of thousands, not just thousands. In one sample of college-aged men, one in sixteen men admitted to raping women they either knew were too intoxicated to give consent, or they used physical force. Among these men who readily admitted to rape but had never been arrested or convicted, they committed an average of six rapes each and proudly described their sexual exploits to the interviewer (Lisak and Miller 2002).

Think of all the illnesses and conditions that make the news regularly. Take gluten intolerance, for example. The incidence for gluten intolerance is somewhere around 1% (more or less, depending on how you define it). Think on how many people you know are gluten intolerant. You know at least one, don’t you?

Now think of the women who have been raped compared to this number – about 17%. There are so many more of us out there who have been affected by sexual assault, unwanted sexual touching, sexual violence, rape and abuse that the number is likely greater than this. And though I display my gluten intolerance every time I ask an annoying, pointed question about a menu item at a restaurant, other ways I and other women identify are not exactly the subject of normal conversation.

And so, you know survivors of sexual assault. You know many of them, in fact, an astounding, upsetting number of them. It is not only normal to know multiple sexual assault survivors, it is normal in our culture for women to be afraid of rape and on the defensive around men for gigantic portions of their lives. And so, even for women who have never and will never be raped, it is a fear-inducing, triggering reminder that our safety is never fully in our own hands.

So let’s turn our attention to some goddamn science.

Allow me to amaze and dazzle you with a very basic reading of a rather clear-cut and unambiguous literature, something Akin could have done even without my fancy PhD. Especially since he is on the Committee on Science, Space, and Technology.

The frequency of legitimate conception

How frequently do raped women get pregnant? It would seem from Akin’s comment that this is a very rare occurrence. However, current evidence suggests it is the same as the pregnancy rate for a single act of intercourse. Ergo, pregnancy from rape occurs as frequently as pregnancy from consensual sex.

A lot of people are citing the Holmes et al (1996) paper that found a 5% pregnancy rate among rape survivors from 12 to 45 years of age. This is a great study that performed several telephone interviews with 4008 participants over three years to determine rates of rape (413 individuals experienced 616 completed rapes, a lifetime incidence of over 13% in this sample) and rates of pregnancy from rape (20 were reported from 19 individuals, or 5%).

In a separate study, Wilcox et al (2001) draw from their amazing prospective dataset from the 1980s where they asked women who were trying to conceive to collect urine every day. They were able to detect hormones, and thus pregnancies and fetal losses, because of these daily urine collections. Work on this dataset from Wilcox, Baird, and others represents the gold standard for our understanding of early pregnancy, fetal loss, and the timing of implantation in the luteal phase of the menstrual cycle. In this paper, the authors are able to show what the possible pregnancy rates are for a given day in the menstrual cycle, taking into account the normal variation many women experience in the length of their cycle and timing of ovulation:

Figure from Wilcox et al 2001 showing chance for pregnancy through the menstrual cycle in women with "normal" and "irregular" cycles.

What they find is that the rate of pregnancy on any given day is about 3.1%, a little lower than the Holmes et al estimate. What Wilcox et al also does well is demonstrate first how the vulnerability to get pregnant varies across the cycle, but also how it is most certainly not zero at the times many of us assume we are not fertile. I’m not sure I am convinced the difference in the rates in these two studies is meaningful, and instead I suspect it is just a result of natural variation based on participant sample. Wilcox et al themselves suggest that the higher number for Holmes et al is a result of methodological differences. But only more studies will help us settle this.

So, rape and consensual sex have the same pregnancy rate. This means that of those 64,080 US rapes in 2004-2005, minus the 15% of rapes that are of children under the age of 12 which gets us to 54,468 rapes of almost all reproductively-aged women, somewhere between 1,689 (3.1%) to 2,723 (5%) pregnancies from rape could have occurred in that year alone. Somewhere around half of those women were probably using some form of hormonal contraception, so let’s hope the numbers are even lower. Unfortunately, access to emergency contraception is still a challenge for rape survivors who go to hospitals, particularly Catholic hospitals, to receive treatment (Smugar et al. 2000).

Legitimate stressors

It’s almost not worth discussing any mechanism that Akin may have dreamed up that allows women to “shut down” a potential conception from rape, now that we see the rates are the same. Except that some people are still trying.

Lest my own words come back to bite me, since I have seen this idea floating through the interwebs I want to address it now: yes, psychosocial stress is associated with fetal loss in some samples. That is not the same thing as saying that stress causes fetal loss. Some women are more reactive to stress than others, and this seems to be based on genes and early childhood experiences. As I pointed out in my post, it certainly isn’t something women have conscious control over. And so it is irrational to link the stress of rape, while awful and severe, to fetal loss, when we understand the mechanism of the stress response and its relationship to pregnancy so poorly, and when we know next to nothing regarding how variation in stress reactivity is produced.

A legitimate word on preeclampsia

And then the always-brilliant Jeremy Yoder and Scicurious pointed me to an older post of Jesse Bering’s that he retweeted today in response to the Akin mess. The gist of the blog post’s argument is that preeclampsia is a mechanism to protect women from unwanted babies with men they don’t know – such as rapists. Bering and others justify this claim with evidence that preeclampsia is more common in women who have not had long-term sexual relationships with the genetic father of the child (as in one night stands, shorter relationships, sperm donors). And that part of it – this correlation between low exposure to the genetic father’s semen and preeclampsia – is indeed born out in the literature.

But.

Preeclampsia is also more common in first pregnancies, with multiples, in obese women and in women over thirty five. And sometimes you get it just because you have shitty luck. In fact, preeclampsia is more common in any of those conditions than it is in women without those risk factors but with shorter sexual relationships with the genetic father. Preeclampsia is a condition where implantation is not deep enough, possibly because the mother has some kind of immune reaction to the fetus. This makes sense with all of the risk factors described above, because all of them stimulate some sort of inflammatory response, which could disrupt implantation (Clancy 2012).

Here’s the other problem. Preeclampsia is not early miscarriage, the only scenario I could imagine where this would become an adaptive mechanism. It is a condition that can lead to very late term miscarriage or stillbirth, not to mention maternal death. The only treatment for preeclampsia, in fact, is to deliver the baby. In industrialized populations this can be done fairly easily, provided the preeclampsia isn’t too severe or the pregnancy is far along before symptoms develop. Under ancestral conditions, women would either have a messy, horrible, late term miscarriage where the baby would die, or if they’re extra unlucky their placenta would abrupt and they too would bleed out and die.

I struggle to see anything adaptive in this. I struggle to see any benefit that could outweigh this cost.

Finally, most perpetrators today are men the victims know. Many, many rapes are part of a broader suite of intimate partner violence behaviors. The idea that preeclampsia could somehow be a pregnancy avoidance mechanism assumes that the rapist is not the woman’s partner, has not in fact had sex, consensual or not, with her for a number of years. It seems likely to me that the kinds of rape we have today are similar to the kinds of rape we had in the ancestral period.

The science behind all of this is straightforward. Akin could have had some assistant or intern look it up in minutes via Google Scholar or PubMed, as a few paper abstracts would have been more illuminating than whatever he was reading. But Akin wasn’t interested in the science, he was interested in how well he could use fear and false information to control women.

In all that powerlessness, that is one thing women have to fight back. When women have the right information they do not have to withstand the claim that they can’t get pregnant from rape, or it must not have been that stressful if they are pregnant. Women and their children who have survived preeclampsia do not have to endure another man telling them that it is a mechanism to avoid rape, or that they could reduce their chances of preeclampsia next time if they’d only swallow. A clear picture of reality dispels the gloom of sexism better than any cleverly worded blog post ever could.

References

Clancy KB. 2012. Inflammation, reproduction, and the Goldilocks Principle. In: Clancy KB, Hinde K, and Rutherford JR, editors. Building Babies: Primate Development in Proximate and Ultimate Perspective. New York: Springer.

Holmes MM, Resnick HS, Kilpatrick DG, and Best CL. 1996. Rape-related pregnancy: Estimates and descriptive characteristics from a national sample of women. American Journal of Obstetrics and Gynecology 175(2):320-325.

Lisak D, and Miller P. 2002. Repeat rape and multiple offending among undetected rapists. Violence and Victims 17(1):73-84.

Smugar S, Spina B, and Merz J. 2000. Informed consent for emergency contraception: variability in hospital care of rape victims. Am J Public Health 90:1372-1376.

Wilcox AJ, Dunson DB, Weinberg CR, Trussell J, and Baird DD. 2001. Likelihood of conception with a single act of intercourse: providing benchmark rates for assessment of post-coital contraceptives. Contraception 63(4):211-215.

(Edited at 7:35am CST to correct error — Akin is a Congressperson, not Senator.)

Kate Clancy About the Author: Dr. Kate Clancy is an Assistant Professor of Anthropology at the University of Illinois. She studies the evolutionary medicine of women’s reproductive physiology, and blogs about her field, the evolution of human behavior and issues for women in science. Find her comment policy here. Follow on Twitter @KateClancy.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. PaulJr 1:33 am 08/21/2012

    I am sorry our society is so evil to women. I apologize to you and all females. If we as a society made certain protections inviolate, then assaulters might think twice. But criminal justice–judges, prosecutors and cops–is broken. Often the guilty go free, the innocent go to prison. We are in difficult times in a difficult nation without clear moral values to protect all.

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  2. 2. jgrosay 9:20 am 08/21/2012

    Rape is a so root act, that imprisoned people hate rapists so deeply that in some cases they kill the rapists in the same prison if they have an opportunity to do it. About the subject of pregnancies after a rape, the year 2000 movie “Mirka”, by Rachid Benhadj and featuring Vanessa Redgrave and Gerard Depardieu offers an original sight of the issue, favorable to the not yet born. The case is recorded about a rapist repeatedly acting in the same neighborhood, and blamed for acts lasting nearly one hour, that some women didn’t reported the rape to the police because “he was a good man”. In Rome and in the 70′s some women rubbed against men in the buses, an action that elicits angry complaints in places such as Egypt from women that suffer this kind of an assault, and they’re right in wanting this to be actively prosecuted and punished. In the 1945 Berlin, a woman, member of the German communist party, she remained hidden to the Nazis, but was raped by the incoming soviet soldiers even when she identified herself as a communist. War corrupts, and it would be good knowing why some people engages in criminal activities such as rape, while others don’t.

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  3. 3. Patrick Clarkin 10:44 am 08/21/2012

    Kate, I’m sorry that Akin’s stupidity compelled you to take on this topic, but I’m glad you did. You hit this out of the park.

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  4. 4. jnrutherford 12:11 pm 08/21/2012

    Kate, this is a wonderful contribution to this discussion. With this issue, we find ourselves confronted by misogynistic belief systems AND extreme scientific illiteracy. Kudos to you for taking both of these on. It’s incomprehensible to me (if I forget the role politics plays and take basic human decency out of the equation) that a memeber of the Committee on Science, Space, and Technology would so audaciously disregard evidence.

    Another sad piece of this that I haven’t seen discussed anywhere yet is that there is a terrible misconception that a woman only gets pregnant if she has an orgasm (um, uterine “upsuck”, anyone?). Therefore, if a woman becomes pregnant she clearly wasn’t raped because obviously she enjoyed it, as we have so frequently been instructed to do if we find ourselves in the inconvenient position of being raped.

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  5. 5. Kate Clancy in reply to Kate Clancy 12:32 pm 08/21/2012

    Thank you Patrick, that means a lot coming from you.

    And thank you too Julienne! Actually, some folks at Double X Science took this on yesterday: http://www.doublexscience.org/2012/08/the-sperm-dont-care-how-they-got-there.html. I should have linked to them, and to Melanie Tannenbaum’s great post as well: http://psysociety.wordpress.com/2012/08/20/just-world-theory/. Well, and a million bazillion other good ones. But those two stick in my mind as some of the best.

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  6. 6. jnrutherford 12:36 pm 08/21/2012

    Thanks for those links, Kate. I should have known that bloggers were on this. Sadly, I’m still mostly a teevee-based news/commentary person and the discussion about the science of this has been pretty poor.

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  7. 7. Kate Clancy in reply to Kate Clancy 12:54 pm 08/21/2012

    I completely understand. I’m more of a blogs person because I like to put my fingers in my ears and say “la la laaa! There are people who care and are doing the right stuff! Surely MSM is doing the same thing! La la laaa!” It doesn’t work that well, unfortunately. MSM keeps ignoring our oh-so-brilliant blogs :) .

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  8. 8. Alejandro1971 1:20 pm 08/21/2012

    Esteemed Dr. Klancy
    Could the actual number of rape-related pregnancies be slightly higher? As you know, peer reviewed studies have suggested that human ovulation is not as concealed as we usually believe and that women appear more attractive when they are ovulating (Personality and Individual Differences (2012, 53:759–763)). Would this make them a more likely target? I would think this should be an argument in favor of emergency contraception.

    Please: to anyone who might miss-understand my statements, I am NOT stating (nor do I believe) that women “provoke” rapists. What I hope to do is call attention to a biological situation (fact?) that should be considered when issuing policy. There is NO justification for rape.

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  9. 9. mairzy.doats 3:48 pm 08/21/2012

    I was butally raped in 1956 and became pregnant. I was told by my father and police that “You must have done something to entice him”.

    Not! He was a family friend whom I tusted. I was young and naive, and scared to death.

    And from then on, treated by society as an outcast because I was pregnant and not married.

    The scars are still here today.

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  10. 10. rightfuture 5:13 pm 08/21/2012

    Thanks for the insights Kate and as carrier of the Y gene I apologise for being a part of a species that somehow finds its use of physical force in the form of rape ‘okay’. And I apologise for sharing the same gene that enables such stupidity in the form of Akin’s comments, which come across to me as a form of excusing the violence inflicted upon so many women.

    Given Akin’s position on the Committee for Science Space and technology, one can best hope (for the future of women and of science) that he resigns quickly from that post
    Marcus Barber
    Australia

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  11. 11. Alejandro1971 6:41 pm 08/21/2012

    @mairzy.doats
    Although I can´t apologize for someone else, I wish I could. Please be assured that many men have come around and would not be as insensitive or brutal as the men whom you dealt with. Unfortunately, I can not write “most men have come around”, there is still a very long way to go. Some places have advanced further, while other seem stuck (I live in Chile, were we seem to surge ahead and the backtrack at double pace).

    If I may, 1956 is the year my mother was 16 years old, yours could have been her story, and I would not put it past my grandfather to react the same way your father did. But today, as a father of three children who can only hope nothing like this ever happens to them, I can tell you that, as I tell them once and again “I am on your side, always”.

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  12. 12. Kate Clancy in reply to Kate Clancy 7:24 pm 08/21/2012

    Hi Alejandro, thanks for your comments, and don’t worry, I didn’t misunderstand you at all. The studies that have examined the timing of rape through the menstrual cycle have found a random pattern, and people who write on it from a more theoretical perspective say that the reason people rape is for power and control, not reproduction. There are some folks who think men rape for reproductive success, but to be honest I don’t think their arguments or evidence are that good. So at least in my opinion, that would not explain higher numbers of pregnancies in women who have been raped.

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  13. 13. Kate Clancy in reply to Kate Clancy 7:24 pm 08/21/2012

    mairzy, I am so sorry to hear this. I hope you have been able to heal, at least a tiny bit, and that your scars get smaller.

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  14. 14. Kate Clancy in reply to Kate Clancy 7:25 pm 08/21/2012

    Marcus, I’m with you! I certainly hope he steps down, but I’m not betting on it.

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  15. 15. davidjaffe 8:33 pm 08/21/2012

    This is just science and hence suspect. Consider the mistakes scientists have made with regard to global warming, evolution, cosmology, paleontology, archaeology, geology, etc. :) .

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  16. 16. Kate Clancy in reply to Kate Clancy 9:08 pm 08/21/2012

    Yes David, we must not get too wrapped up in the scientific method! ;)

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  17. 17. tierrasimbolica 9:29 pm 08/21/2012

    The following study published in 2003 found that incident of pregnancy was much higher in rape victims than in cases of consensual sex:

    http://www.springerlink.com/content/wp5cnp43k6byxj4d/

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  18. 18. upixiqu 6:16 am 08/22/2012

    Thanks Kate. This is a phenomenally interesting post. I was recently facilitating a human rights training for church workers and used a similar scenario to explain some fundamental concepts. It was interesting to hear arguments similar to Akin’s but to be fair, these are mostly illiterate workers who live in one of the most remote parts of the world without access to scientific information. But to actually read about a Congressperson, and no less than a members of Committee on Science, Space, and Technology say this is shocking.

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  19. 19. cswagner 9:06 am 08/22/2012

    All I can say is: thank you, Dr. Clancy.

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  20. 20. redwngfarmer 9:38 am 08/22/2012

    Kate, thank you for this . I am outraged by Akin ( Im Male and in health care) and this issue must not be allowed to die as its newsworthiness _ fickle at best – wanes . Add to the mentality that permits such asshole thinking as pro life insanity and religions intransiece against contraception, we have social evil of cosmic proportion

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  21. 21. ErinW 10:10 am 08/22/2012

    I’m writing a letter to Todd Akin to both explain to him that it’s better to admit you don’t things than to lie and to educate him on rape. Would it be all right if I printed out your blog post and included it in the letter (with attribution of course).

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  22. 22. Kate Clancy in reply to Kate Clancy 10:24 am 08/22/2012

    Hi tierrasimbolica, my understanding is that that paper was written by an English and Economics teacher, so not biologists. There are also a lot of problematic assumptions in their calculations. If I get to it later this week, I actually plan on writing something about it.

    upixiqu, cswagner, redwngfarmer, thank you very much. And ErinW, yes, you can absolutely send the post along.

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  23. 23. donAlvar 10:31 am 08/22/2012

    Member of the Commission on Science, Space and Technology. Yet another reason to be proud for those few Americans that actually know there is an outside world poking fun at their great nation. It might seem unfair to say that, but hey, it is a democracy, is it not?

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  24. 24. tierrasimbolica 11:00 am 08/22/2012

    Hi Kate, I’d be interested in hearing your further assessment. Their field of study is not to their discredit if the analysis of the research happens to be sound and valid. One site says, “As to why rape victims would have a higher rate of pregnancy, the Gottschalls put forward a few theories. They look at previous research, which suggests that men are more attracted to women who are fertile and ovulating. In consensual sex, women can decline sex at a time where there might be a high likelihood of pregnancy. That’s not the case in rape.” It also says, “The Gottschalls do acknowledge that their study was at odds with previous research, which showed a lower rate of pregnancy among rape victims.” Their reasoning makes sense to me but if you will be posting some counterarguments, I look forward to checking it out.

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  25. 25. tierrasimbolica 11:07 am 08/22/2012

    As a side note, I understand that someone with education in biology would hold an opinion of greater weight, but this is not to say that an English or Economics professor is incapable of using logic to do statistical analysis. In any case, I will be on the lookout for your counterarguments to their assertions.

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  26. 26. Kate Clancy in reply to Kate Clancy 11:18 am 08/22/2012

    Hi tierrasimbolica, you’re right and I shouldn’t be so quick to judge based on their having a different academic background. I also like and respect the journal Human Nature, but sometimes it seems like that journal is where wacky ideas go to get published. So part of my bias is, I think, also based on my hesitancy to trust some of the weirder stuff that comes out of that journal. In any case, I promise to get to it later this week if I manage to get a grant written first :) .

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  27. 27. marz62 5:18 pm 08/22/2012

    Dr. Clancy:

    You wrote: “But Akin wasn’t interested in the science, he was interested in how well he could use fear and false information to control women.”

    This stands out as a completely non-scientific opinion in an otherwise welcome and scientifically valid article. As a female lawyer pointed out to me just this morning, rejecting the right to abortion in cases of rape-related pregnancy is morally consistent with the ‘right to life’ position.

    Mr. Akins may have been using faulty science (or anti-science), but his motivation for doing so could have been a sincere (though misinformed) rationalization for his moral stance: that all unborn life is still life, is valuable and has a right to be, regardless of the cause of that life.

    If one is a ‘right to lifer’, then how does one justify making an exception in the case of rape? This exception would become morally ambiguous. I suspect that, due to the heinous nature of the crime of rape, many anti-choice proponents prefer not to allow said heinousness to cloud their strong (absolutist) stance, and so try to rationalize this by concocting an automatic “shut down” response in “legitimately” raped women.

    Sure, the belief by Akin (and others) is wrong (and viewed as incredibly callous/insensitive to the rape victim by liberals), but so is your assumption of his underlying motive(s).

    We may not like it, or agree with it, but the rejection of an exception allowing for abortion in the cases of rape or incest — from the Right to Life viewpoint — is morally consistent…however simplistic.

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  28. 28. noretreat 7:29 pm 08/22/2012

    “…I believe deeply in the protection of all life…”

    With the exception of capital punishment, of course. Hypocrite.

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  29. 29. westendal 8:13 pm 08/22/2012

    Perhaps Mr. Akin has been in Congress so long he thinks he can change the laws of nature, or just make them up as needed.

    The scary thing is that guys like that, by which I mean militantly ignorant, can be clever enough to convince people to vote for them.

    There may well be something about politics, especially in recent years, that attracts folks like that.

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  30. 30. d_an1 9:54 pm 08/22/2012

    marz62 you are very confused. So let me spell it out for you. There is a difference between intentions/rationalizations and actions. Actions are something that you do. Intentions/rationalizations are the reasons why you do something.

    Sure Akin rationalizes his actions with his prolife ideology, but it would be pretty silly to deny that the actions do have the effect of preventing women from taking full control over their reproductive capacities. So the effect of his actions is to tell women what they can or cannot do with their own bodies…that is control no matter how you cut it. Kate was commenting on his actions not his motive.

    Further, in order to carry out his actions Akins had to rely on fear and false information. This was simply a comment on the methods he chose to carry out his actions. (Again, not a comment on his intention/rationalizations). You certainly agreed that he used “faulty science” so I shouldn’t have to explain the point about false information. The fear is a little bit harder to explain. Since I do not want to write a book just understand that it comes from the history of how rape has been viewed in the past. These kinds of ideas do pass on blame wholly to the victim of the crime and because it is the victim’s fault then we should treat them as if they did something wrong. If this is a social norm then it is out of fear that women do not speak against what people like Akin say. Consult a history book, it should be able to enlighten you on how people who have been raped were treated in the past. Ideas like this were so entrenched in our society that attitudes didn’t start to change until women had another sexual revolution. They had to literally protest society itself in order to get things moving.

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  31. 31. Glendon Mellow 2:00 am 08/23/2012

    “So let’s turn our attention to some goddamn science.”

    This whole post is epic, Kate. When I got to that line I was ready to yell, “Yeah! Drop science on those bastards!”

    And then you did.

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  32. 32. Kate Clancy in reply to Kate Clancy 10:27 am 08/23/2012

    Thanks Glendon! And rock on, d_an1.

    If anyone reading here has realized that their comment has not made it through moderation and it’s been more than a few hours (not including comments overnight), you may want to consider re-reading this post and the comments policy: http://blogs.scientificamerican.com/context-and-variation/2012/01/24/blogging-while-female/.

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  33. 33. sciliz 11:29 am 08/23/2012

    Marz62- Akin’s motivation can be completely sincere, and it could result in him spreading misinformation and fear. And his motivation does appear to be to control women who are deciding to have abortions.

    The intensity or sincerity with one holds a conviction does not impact the purity of the tactics employed to achieve a political goal. I certainly don’t doubt the intensity or sincerity of the convictions of the right-to-life terrorists who set off bombs in clinics.

    Kate- For my own political views, it’s irrelevant, but I’m not understanding the numbers here.
    I’m not sure what to make of the 32,000 pregnancies from rape/year that people are associating with the Holmes et al 1996 (for example, http://www.cdc.gov/violenceprevention/sexualviolence/consequences.html).

    That isn’t possible if the total is 64,000 rapes (though part of it could be that the rate of rape has decreased that much between 1996ish and 2004ish?). But 1,700 is pretty different from 32,000.

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  34. 34. Kate Clancy in reply to Kate Clancy 11:36 am 08/23/2012

    Hi sciliz – I agree that the numbers don’t work. I used RAINN’s stats, Holmes et al uses something different. I have a follow-up post on this here: http://blogs.scientificamerican.com/context-and-variation/2012/08/21/what-do-you-do-when-there-is-no-best-dataset-a-follow-up-on-pregnancy-and-rape-statistics/. It’s still pretty unsatisfying, though.

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  35. 35. atomicdog 5:20 pm 08/24/2012

    Hi Kate,

    Was the 5% pregnancy rate just calculated by dividing 20 (number of pregnancies from rape) by 413 (number of individuals who were raped)? Since we are talking about per incident chance of getting pregnant from rape, shouldn’t the number be 20/616 (number of completed rapes) which yields a rate of 3.24% which is surprisingly close to the 3.1% figure you cite in the Wilcox study.

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  36. 36. Kate Clancy in reply to Kate Clancy 5:23 pm 08/24/2012

    I agree, atomicdog, that that would be a better read of the data. As much as I love the Holmes et al paper and the amazing dataset they collected, I do kinda wish they had done a better job with their own analysis.

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  37. 37. atomicdog 9:02 pm 08/24/2012

    After doing some more reading on the topic I found this article on the BBC (The article for some reason comes up with a 5% chance of pregnancy for a single act of unprotected sex, but I think that’s wrong or just a really rough summary of the results)

    http://www.bbc.com/future/story/20120313-sex-in-the-city-or-elsewhere

    http://www.demographic-research.org/volumes/vol3/5/3-5.pdf

    The article cites a European study from 2000 of 782 couples and followed their chance of getting pregnant when they had unprotected sex once during a 12 day fertility window of each menstrual cycle. A lot of data and results were collected, but one very interesting piece of data was that they ultimately got results of 487 pregnancies out of 6724 cycles (or a rate of 7.2%).

    If an average menstrual cycle is 28 days and you calculate the odds of a random act of unprotected sex during this the cycle falls in the 12 day window (12/28) multiplied by the chance of getting pregnant (487/6724), you come up with 3.1% which is exactly inline with the Wilcox study.

    Just thought this might be interesting!

    Link to this

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