Monday, October 25, 2010

How does an anthropological perspective contribute to our understanding of birth control? Part I

I polled my Twitter followers recently to find out what they wanted me to cover, and heard back a resounding "CONTRACEPTIVES!" So first I am going to re-post a series I wrote on my lab blog in July of 2009, with significant editing and updating. I think after these reposts I'll have a better idea of where it would make sense for me to contribute more, if at all. This is post one of five.
I am not a medical professional. I am a PhD, not an MD, so this is not medical advice. And in fact, I am quite sure there are anthropologists out there who do not share my opinion, so this is not even anthropological advice. This is just one person’s perspective on a medication so pervasive few people even think of it as the serious prescription that it is.

Hormonal birth control has been around for many decades, and has seen many improvements, reductions in dosage, and different ways of accessing the medication, from a shot, to a patch, a ring or a pill. Hormonal birth control is used off-label for mood stabilization and acne, and increasingly these contraceptives are also approved for these non-contraceptive purposes. You’ve probably seen the ads of skinny-armed women punching at “irritability” and “bloating” in bubble letters before them with a girly rendition of “We’re not gonna take it” in the background. You’ve seen the slightly more “empowered” ads that have cropped up recently regarding the hormonal contraception that you can take continuously to avoid your period, where far stronger women are staring right into the camera and daring you to doubt their decisions.

I worry about health and safety issues related to hormonal contraceptives when I see these ads, because they are 1) focusing on the non-birth control aspects of the drug in order to increase the number of consumers and 2) trying to frame the debate about contraception with a watery version of "choice" feminism. However, how one feels about a commercial is not a good enough reason to dismiss a medication used by a huge fraction of reproductively aged women in the US. I was recently annoyed by a Tylenol ad, but I give my daughter acetaminophen when she has a very high temperature (not when she has a mild one -- but that's a whole other issue!). I am able to get off my high horse, folks, and I’d like to do that to discuss some recent evidence around hormonal contraception. This post will cover contraindications and side effects for hormonal contraceptives. The other posts will cover variation in menstrual cycling; population variation and environment; hormones, behavior and cognition; and non-hormonal contraceptive options.


If you read the packaging and/or you have a doctor worth his/her salt, you know if you have high blood pressure, a history of blood clots or liver dysfunction, you should not take hormonal contraception. End of story, and don’t try to get around it.

But do you know that if your BMI is over 25 you are at an increased risk of unintended pregnancies? The dosage for hormonal contraception was designed for average to low-average weight women from developed countries (the issue of developed versus developing countries will be important in later posts). Brunner Huber and Hogue (2005) found that contracepting overweight and obese women had twice the odds of an unintended pregnancy compared to normal weight women. The authors surveyed women after they had given birth and asked if the pregnancy was intended or unintended, and whether the individuals had used contraception or not. Among contracepting women, the number of overweight and obese women with unintended pregnancies was much higher than those with intended pregnancies. Further, they cite a convincing literature and provide a credible mechanism for why overweight women tend to have reduced efficacy on hormonal contraceptives. Burkman et al (2009) recently found similar results, but the relationship was not quite statistically significant. The results do seem to vary somewhat with which contraceptive is being tested. But with the average American woman’s BMI at 28, it seems as though today’s oral contraceptives may not be effective for a majority of our country’s population.

There are two other major issues to consider regarding the effects of hormonal contraceptives on health. The first is that hormonal contraceptives negatively impact bone mineral density. Last year, one of my undergrads Emily Marzolph wrote a wonderful Honors paper for me entitled "Moderate changes to bone mineral density due to hormonal contraceptives during adolescence may undermine wide array of skeletal mass diversity." In her literature review, she found significant evidence that hormonal contraceptives, particularly the progestin-only injection Depo-Provera, lower bone mineral density rates (e.g., Cromer et al 2005, Prior et al 2001). However, to put these results in context, Emily also looked at what we know of interpopulational variation in bone mineral density; this turns out to be quite significant as well. Analyzing these data qualitatively, it appears that the reduction in bone mineral density caused by hormonal contraceptives is still within the range of variation seen across populations (Arabi et al 2004, Hou et al 2007). Here's a free dissertation topic for you: someone ought to do a meta-analysis of this literature, or a cross-populational analysis of new data, that examines the differential effects of ethnicity, environment and hormonal contraceptives on bone mineral density! Who knew you could get free dissertation advice from a blog?

The second health issue I want to mention is the potential increase in systemic inflammation with the use of hormonal contraceptives (one of my other undergraduates, Katherine Tribble, found this article for our lab's weekly journal club). Morin-Papunen et al (2008) looked at women at thirty one years of age in the Northern Finland Birth Cohort, born in 1966. They grouped these women into levonorgestrel-releasing intrauterine device (IUD) users, oral contraceptive users, and no hormonal contraception use. Morin-Papunen et al (2008) found oral contraceptive usage was correlated with increased C-reactive protein concentrations -- this is a biomarker for inflammation that is associated with cardiovascular disease. Compared to IUD users, oral contraceptive users also had more insulin resistance, higher blood pressure, raised lipids and insulin levels, despite having a smaller waist and lower waist-hip ratio (a larger waist or higher waist-hip ratio is often associated with these results). Further, most of these results actually strengthened when factors like BMI, household income, and alcohol consumption were controlled for. Another interesting point, third generation hormonal contraceptives, which are lower concentrations of synthetic hormones than the second generation, actually had higher serum levels of insulin, CRP, total cholesterol and other lipids, compared to users of second generation contraceptives.

So in addition to the factors you already knew about, you may want to avoid hormonal contraceptives if your BMI is over 25 and are using them for contraception; or, if you are already at risk for osteoporosis or cardiovascular disease (or want to reduce your risk for these things).

In the second post, I’ll discuss what it means to have a normal menstrual cycle, and how this relates to the prevalence of hormonal contraceptives.


Arabi, A., Nabulsi, M., Maalouf, J., Chouchair, M., Khaliffe, H., Vieth, R., & Elhajjfuleihan, G. (2004). Bone mineral density by age, gender, pubertal stages, and socioeconomic status in healthy Lebanese children and adolescents Bone, 35 (5), 1169-1179 DOI: 10.1016/j.bone.2004.06.015

Brunner Huber, L., & Hogue, C. (2005). The Association Between Body Weight, Unintended Pregnancy Resulting in a Livebirth, and Contraception at the Time of Conception Maternal and Child Health Journal, 9 (4), 413-420 DOI: 10.1007/s10995-005-0015-5

Burkman RT, Fisher AC, Wan GJ, Barnowski CE, & LaGuardia KD (2009). Association between efficacy and body weight or body mass index for two low-dose oral contraceptives Contraception, 79 (6), 424-427.

Cromer BA, Lazebnik R, Rome E, Stager M, Bonny A, Ziegler J, & Debanne SM (2005). Double-blinded randomized controlled trial of estrogen supplementation in adolescent girls who receive depot medroxyprogesterone acetate for contraception. American journal of obstetrics and gynecology, 192 (1), 42-7 PMID: 15672001

Hou YL, Wu XP, Luo XH, Zhang H, Cao XZ, Jiang YB, & Liao EY (2007). Differences in age-related bone mass of proximal femur between Chinese women and different ethnic women in the United States. Journal of bone and mineral metabolism, 25 (4), 243-52 PMID: 17593495

Morin-Papunen L, Martikainen H, McCarthy MI, Franks S, Sovio U, Hartikainen AL, Ruokonen A, Leinonen M, Laitinen J, Järvelin MR, & Pouta A (2008). Comparison of metabolic and inflammatory outcomes in women who used oral contraceptives and the levonorgestrel-releasing intrauterine device in a general population. American journal of obstetrics and gynecology, 199 (5), 5290-2147483647 PMID: 18533124

Prior JC, Kirkland SA, Joseph L, Kreiger N, Murray TM, Hanley DA, Adachi JD, Vigna YM, Berger C, Blondeau L, Jackson SA, & Tenenhouse A (2001). Oral contraceptive use and bone mineral density in premenopausal women: cross-sectional, population-based data from the Canadian Multicentre Osteoporosis Study. CMAJ : Canadian Medical Association journal = journal de l'Association medicale canadienne, 165 (8), 1023-9 PMID: 11699697


  1. Hi, Dr. Clancy!

    I found this post through, and was very excited to see you're doing a series on this topic.

    I wonder, though: does the thing about reduced efficacy in larger women hold true even for combination (estradiol + a progestogen) pills? I knew it was an issue for progestin-only pills, but this will be the first I've heard that it's also a problem for the combination pill!

  2. Hi Lindsay, welcome! The Brunner Huber and Hogue article does not specify type of contraceptive but also cites an additional article about combined contraceptives and body weight that supports their findings. The Burkman et al article is specifically about combined estradiol/progesterone pills as well. I don't think you're the only one who didn't know about this association!

  3. Here's the thing that bugs me- if hormonal contraception was totally not effective for a majority of the population, *this would not be news to anyone*. We'd already all know about it because we (those of us who have used the pill for years) would have gotten pregnant. I don't have the medical/statistical knowledge to figure out how much it's really working. Twice the odds of getting pregnant? Does that mean that if it's 99% effective for normal weight women it's 98% for overweight women? That's still a whole lot better than nothing.