What Now? Understanding EC Efficacy and Body Weight

Taken from the March/April 2016 issue of the Women's Health Activist Newsletter.

For women who need EC and are interested in a long-acting method, the copper IUD is nearly 100 percent effective when provided after sex and provides up to 12 years of on-going contraceptive protection.1 Options are expanding, and this is fantastic news for anyone who needs EC.

What’s not so fantastic news is the possibility that EC pills may not be as effective for some women, depending on their weight. Research published in 2011 sparked vigorous debate – and some regulatory changes – when it reported that levonorgestrel EC pills may be ineffective for women who weigh at least 154 pounds, and that ulipristal acetate EC pills may be ineffective for women who weigh 194 pounds or more.2

Based on this study (and further analyses of the same data), in late 2013, the European Medicines Agency (EMA) approved a change to the label for NorLevo, a levonorgestrel EC product available in Europe. The new label warned that “in clinical trials, contraceptive efficacy was reduced in women weighing 75 kg [165 lbs] or more and levonorgestrel was not effective in women who weighed more than 80 kg [175 lbs]”.3 Health Canada, the Canadian regulatory authority, quickly authorized the same change.

Studies conducted by the World Health Organization (conducted among populations of African and Asian women) found no relationship between EC efficacy and weight, however.4 So, a few months later (July 2014) the EMA reversed the label change, announcing that “the data were too limited and not robust enough to conclude with certainty that contraceptive effect is reduced with increased bodyweight” and removed the warning.5 The Food and Drug Administration (FDA) has not made any similar changes.

So where does this leave us? Different studies came to different conclusions; there are important limitations to the available data;6 and the EMA reversed its labeling changes after further review.

Pregnancies are relatively rare in EC studies, which means that it can be challenging and expensive to conduct a study to detect differences based on specific characteristics, such as weight. It is possible, and perhaps likely, that definitive data on this question will never be available. But, that doesn’t mean we should disregard these findings. Even if we don’t have clear-cut answers to whether there is a weight threshold at which EC pills become ineffective (or less likely to be effective), we should consider that there may be a relationship between the efficacy of an EC product (especially levonorgestrel EC pills) and the weight of the woman using it. Given that the average American woman weighs 166 pounds,7 this potentially affects millions of women in the U.S.

If all EC options were equally accessible, the simple solution would be to recommend that women use the more effective EC methods. But, it’s not so simple in reality. The copper IUD is by far the most effective EC method, but not all women want (or can get) an IUD right away. Ulipristal acetate seems to be more effective than levonorgestrel for all women, regardless of their weight, because it works closer to the time of ovulation.8 But, both of these methods are provider-dependent, and a recent study shows that the majority of health care providers who treat women of reproductive age haven’t heard of and don’t offer these methods.9 Levonorgestrel EC is available over-the-counter without restrictions, but it is expensive ($40-50 per dose) and availability is inconsistent. Many pharmacies don’t stock the product on the shelf and some still ask (illegally) for proof of age.10 Despite these challenges, levonorgestrel EC is the easiest method for most women to get quickly — of critical importance for EC pills, which work by preventing or delaying ovulation and should be taken as soon as possible after unprotected sex.

The bottom line is that weight might be a factor in whether EC will work for a particular woman, but timing definitely is. All women (and, perhaps, particularly women with higher body weight) should be encouraged to use the most effective EC options (the copper IUD or ulipristal acetate). But if these options are unacceptable or not quickly accessible, no woman should be denied or discouraged from using levonorgestrel EC because of her weight.

Kelly Cleland is a researcher at Princeton University and the Executive Director of the American Society for Emergency Contraception.

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1. Cleland K, Zhu H, Goldstuck N, et al., “The efficacy of intrauterine devices for emergency contraception: a systematic review of 35 years of experience,” Hum Reprod 2012; 27:1994-2000.

2. Glasier A, Cameron ST, Blithe D, et al., “”Can we identify women at risk of pregnancy despite using emergency contraception? Data from randomized trials of ulipristal acetate and levonorgestrel,” Contraception 2011; 84:363-7.

3. Health Products Regulatory Authority (HPRA), Norlevo 1.5mg, summary of product characteristics, Dublin: HPRA, January 23, 2014. Available online at: www.imb.ie/images/uploaded/swedocuments/LicenseSPC_PA1166-002-001_28112013160052.pdf.

4. Gemzell-Danielsson K, Kardos L, von Hertzen H, “Impact of bodyweight/body mass index on the effectiveness of emergency contraception with levonorgestrel: a pooled-analysis of three randomized controlled trials,” Current Medical Research and Opinion 2015; 31(12):2241-8. Epub 2015 Oct 27.

5. European Medicines Agency (EMA), Press Release: Levonorgestrel and ulipristal remain suitable emergency contraceptives for all women, regardless of bodyweight, London: EMA, July 24, 2014. Available online at: www.ema.europa.eu/ema/index.jsp?curl=pages/news_and_events/news/2014/07/news_detail_002145.jsp&mid=WC0b01ac058004d5c1.

6. Cleland K, Wood S, “A tale of two label changes,” Contraception 2014; 90:1-3.

7. Fryar CD, Gu Q, Ogden CL, “Anthropometric reference data for children and adults: United States, 2007–2010,” Vital and Health Statistics 2012; 11(252):1-48.

8. Glasier AF, Cameron S, Fine P, et al., “Ulipristal acetate versus levonorgestrel for emergency contraception: a randomised non-inferiority trial and meta-analysis,” Lancet 2010; 375:555-62.

9. Batur P, Cleland K, McNamara M et al., “Emergency Contraception: A multispecialty survey of clinician knowledge and practices,” Contraception 2016; 93(2):154-52.

10. The American Society for Emergency Contraception (ASEC), Inching Towards Progress: ASEC’s 2015 Pharmacy Access Study, Princeton (NJ): ASEC, 2015. Available at www.americansocietyforec.org.