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Contraceptive Pearl: Discussing Emergency Contraception & Weight

Written by Samantha Hyacinth

We are able to offer patients more options for emergency contraception (EC) than ever before. Now, those who have unprotected sex or a contraceptive failure can choose between 1.5 mg levonorgestrel, 30 mg ulipristal acetate (UPA), the copper IUD (Cu-IUD), and the 52 mg levonorgestrel IUD (LNG-IUD). Unfortunately, not all of these options are equally effective. In light of pharmacokinetic studies¹ and pooled analyses from randomized controlled trials2-4 done within the past two decades, there is particular concern that some EC options are less effective for people with a BMI >30. Because of the concern over levonorgestrel in particular, some health centers have adopted policies of only offering UPA or a Cu-IUD to people within a certain weight category. But, due to the lack of robust data specifically looking at pregnancy outcomes by BMI for people taking EC, these interventions may have been issued prematurely. Because these decisions have often led to providers limiting EC options for patients above a certain BMI, it is important for us to question whether those limitations on patient choice are truly necessary.

Most of the data we have on weight and EC efficacy is on levonorgestrel, there are fewer studies on UPA.⁵ Currently these efficacy studies fall into two categories, pharmacokinetic studies and retrospective data analyses. The former looks at differences in how the bodies of obese and non-obese people metabolize the medication (the studies all defined obesity as BMI >/=30 and non-obese as a BMI <30). One such study⁴ found that due to differences in metabolism the obese participants were exposed to lower doses of levonorgestrel, but similar doses of UPA as compared to non-obese participants given the same dose orally. The limitations of any pharmacokinetic study is that they cannot tell us whether these differences in drug metabolism lead to a difference in pregnancy outcomes for the two groups of participants. This study in particular mentions the need for pharmacodynamic studies to determine the concentrations of levonorgestrel and UPA that lead to ovulation inhibition.

The other class of studies that we have access to are retrospective data analyses. These are studies that use data from older studies that examined the efficacy of levonorgestrel and UPA either on their own or in comparison to other methods of EC. Although these studies often include data on participants’ weight, they were not initially designed to study the impact of weight on EC’s efficacy. But, researchers are able to go back and use the participant data from these studies to see which variables have an impact on pregnancy outcomes. Some of these studies5,6 have shown that for both oral levonorgestrel and UPA, there is an increased risk of pregnancy for obese vs non-obese participants. One major limitation of the initial efficacy studies from which the data was taken is that these studies have small numbers of obese participants and small numbers of people who become pregnant after taking EC. Many of these retrospective data analyses examine data from the same World Health Organization (WHO) studies,7-9 one of which contained a group of 60 outliers who represented 1% of the sample and 6.8% of pregnancies. This group of participants was mostly categorized as overweight and obese with only 4/60 being categorized as underweight or of normal weight. In a retrospective analysis conducted by Lazlo Kardos,10 removal of these outliers erased the discrepancy in EC efficacy between obese and non-obese participants.

With the data we currently have access to, it is hard to definitively say if oral levonorgestrel and UPA are less effective at preventing pregnancy when used by people with higher weights/BMIs. Both the American Society for Emergency Contraception and the European Medicines Agency agree that no one should be refused or discouraged from using any form of EC based on weight.  As providers, one of the most transparent things we can do when faced with uncertainty is to share it with our patients. Rather than limiting our patients’ choices for EC, we can be honest about what we do and don’t know. And remember that although we as providers tend to prioritize efficacy over all else, our patients may have different concerns such as cost, accessibility, side effects, etc.

Before having any conversation about a patient’s weight, remember how harmful fatphobia is, and the fact that we are all inundated with negative messages about existing in larger bodies. When explaining to a patient that EC may be less effective due to their BMI, there is a lot of potential for that patient to feel that they are to blame. Do not use these conversations as an entry into a conversation about weight loss. Instead, here are a few tips for talking to patients about their weight and EC:

  • Both levonorgestrel and UPA may be less effective for those with a BMI >30. This effect, if it exists, may be less pronounced for those taking UPA.
  • Discuss the contradictory data, explain that we don’t yet have the ideal studies to get us the answers that we need.
  • Patient-centered care means the patient’s priorities matter most. Do not assume that efficacy is what matters most for that patient.
  • Explicitly tell all of your patients that the fault lies with the drug companies for not ensuring that their medication works for people in all different kinds of bodies. Your patient is not wrong for simply existing in their body.
  • Do not use this information to encourage patients to lose weight.

RHAP resources:

Your Birth Control Choices Fact Sheet

Emergency Contraception: Which EC is Right for Me?


Non-RHAP resources:

ASEC – Efficacy of Emergency Contraception and Body Weight: Current Understanding and Recommendations

Emergency contraceptives | European Medicines Agency

FSRH Guideline Emergency Contraception

Levonorgestrel emergency contraception and bodyweight


1. Praditpan P, Hamouie A, Basaraba CN, et al. Pharmacokinetics of levonorgestrel and ulipristal acetate emergency contraception in women with normal and obese body mass index. Contraception. 2017;95(5):464-469. doi:10.1016/j.contraception.2017.01.004

2. Festin MPR, Peregoudov A, Seuc A, Kiarie J, Temmerman M. Effect of BMI and body weight on pregnancy rates with LNG as emergency contraception: analysis of four WHO HRP studies. Contraception. 2017;95(1):50-54. doi:10.1016/j.contraception.2016.08.001

3. 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. Curr Med Res Opin. 2015;31(12):2241-2248. doi:10.1185/03007995.2015.1094455

4. Moreau C, Trussell J. Results from pooled Phase III studies of ulipristal acetate for emergency contraception. Contraception. 2012;86(6):673-680. doi:10.1016/j.contraception.2012.05.012

5. 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(4):363-367. doi:10.1016/j.contraception.2011.02.009

6. Jatlaoui TC, Curtis KM. Safety and effectiveness data for emergency contraceptive pills among women with obesity: a systematic review. Contraception. 2016;94(6):605-611. doi:10.1016/j.contraception.2016.05.002

7. Regulation TFoPMoF. Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. The Lancet. 1998;352(9126):428–433.

8. von Hertzen H, Piaggio G, Peregoudov A, et al.. Low dose mifepristone and two regimens of levonorgestrel for emergency contraception: a WHO multicentre randomised trial. The Lancet. 2002;360(9348):1803–1810.

9. Dada OA, Godfrey EM, Piaggio G, et al.. A randomized, double-blind, noninferiority study to compare two regimens of levonorgestrel for emergency contraception in Nigeria. Contraception. 2010;82(4):373–378.

10. Kardos L. Levonorgestrel emergency contraception and bodyweight: are current recommendations consistent with historic data?. J Drug Assess. 2020;9(1):37-42. Published 2020 Feb 10. doi:10.1080/21556660.2020.1725524


The Reproductive Health Access Project does not accept funding from pharmaceutical companies. We do not promote specific brands of medication or contraception. The information in the Contraceptive Pearls is unbiased, based on science alone.