Does body weight change how effective EC is?

What you need to know about the current research and how to talk to patients.

by Kelly Cleland, MPA, MPH

published 02/18/20

Questions about emergency contraception (EC) efficacy and weight spiked last year after Annie, the lead character on Hulu’s Shrill who weighs more than 165 pounds, gets pregnant despite having taken levonorgestrel (LNG) EC. This episode led to a media outcry about why information about the connection between EC and weight hasn’t been more widely available and why this was the first time they’ve heard this connection being discussed in the public arena. Addressing questions about the connection between EC and weight are of pressing concern because the average woman of reproductive age in the US weighs 168 pounds. But for providers this isn’t really a new discussion—in 2013, a similar conversation was prompted when the European Medicines Agency (the European equivalent to the US FDA) changed the label for NorLevo (a 1.5mg LNG EC with the same dose as Plan B One-Step and generics) to warn that it doesn’t work for people over 176 pounds. They reversed that labelling the following year after further analysis of the data, and the FDA considered, but never made, such a change. This left EC users and providers adrift in a sea of inconclusive information when it comes to the effectiveness of LNG EC for users with higher than average body weight.

So, what is the current evidence?

Some of the confusion about effectiveness of EC methods is due to the fact that the existing data strongly suggest a relationship between efficacy and weight, but they’re not conclusive and there are no completed clinical trials that specifically measure this relationship. So, we are left to make recommendations based on the studies that we have: large clinical trials with few pregnancies, small numbers of EC users in the higher weight categories, and self-reported weight. The best available evidence suggests that LNG EC may be less effective for users who weigh 165 pounds or more, and ineffective for those weighing 176 pounds or more. These studies also found that ulipristal acetate (UPA) EC, brand name ella, may be ineffective for users who weigh 196 pounds or more. We do know that weight doesn’t change how effective a copper IUD is for EC.

Emerging evidence suggests that doubling the dose of LNG EC for people with body mass index (BMI) of 30 kg/m2 or greater may be a reasonable approach. (Note: it might be confusing for providers and patients to switch between weight and BMI, but studies are not consistent in using one measure or the other which further complicates how we talk about the evidence and make recommendations.) In one study, the serum concentration of LNG after taking a standard 1.5 mg dose was about 50% lower in people with BMI greater than 30 kg/m2, compared with those with BMI less than 25 kg/m2. Doubling the dose of LNG EC (from 1.5 mg to 3.0 mg) in the higher-BMI group produced serum concentration levels similar to those in lower BMI group who had taken the regular dose (1.5 mg). This is a small pharmacokinetic study that did not measure endpoints more directly related to effectiveness, like ovulation or pregnancy, and it doesn’t directly recommend using the double dose of LNG. However, based on this study some guidelines do recommend a double dose of LNG EC when other options are not available.

This American Society of Emergency Contraception (ASEC) statement details recommendations for providers based on the most current research.

Balancing effectiveness and access

Health care providers must balance the very real possibility that LNG EC may not work for individuals who weigh more than 176 pounds with the on-the-ground challenges of accessing EC. Although access to LNG EC is far from perfect, it is the easiest form of EC to get because it is approved for over-the-counter (OTC) sale. UPA EC has been approved in the US since 2010, but it’s only available by prescription and many health care providers still don’t know about it—a 2016 study found that 29% of healthcare providers had heard of UPA EC, and only 7% provide it. In addition, few pharmacies keep UPA in stock, a recent study found that less than 10% of pharmacies in 10 major US cities were able to immediately fill a prescription for UPA. These barriers mean that someone may not be able to access UPA in time for it to be effective. A copper IUD is the most effective option for EC regardless of how much you weigh, but they may not be ideal for all patients because they require a procedure by a trained health care provider that some may find invasive or uncomfortable. Copper IUDs may be cost-prohibitive for uninsured patients, and while they can be used as ongoing birth control, they may cause heavier periods with more cramping for users.

Counseling patients with higher body weight about EC

When counseling patients, it may be helpful to focus conversations on the limitations of EC rather than on their weight. And it can help to use objective and non-judgmental language, like, “Unfortunately, we don’t have conclusive evidence about the effectiveness of this medication in people with different body sizes. For people who weigh 165 pounds or more, we don’t know for sure whether it’s as effective.” In general, offer the most accessible and effective method of EC for your patient based on weight and preferences by engaging in shared-decision making about EC methods. And no one should be denied access to any EC method simply because of weight. Here are some key facts and questions that can help guide conversations about EC:

  • The copper IUD is the most effective method regardless of weight, but is your patient interested in a long-acting method? Can you offer them a copper IUD today? Would a heavier period with more cramping be acceptable? Can they afford an IUD today?
  • If your patient is not interested in an IUD or you are not able to place an IUD today, offer a prescription for UPA EC, the most effective EC pill for people who weigh less than 195 pounds. But is there a pharmacy in your area that stocks UPA EC? Can they get the medication in time? Can they afford it? And consider offering a prescription for UPA EC to help people have it on hand when they need EC. Did you know your patients can even get ella delivered to their door after a quick online consultation with a provider?
  • If UPA EC is not available and your patient weighs more than 175 pounds, consider suggesting a double dose of LNG EC. While this recommendation is based on pharmacokinetic data alone, it is safe to use, and it may increase the effectiveness. Consider offering a prescription (which makes it more likely that insurance will cover it) and recognize that the patient may need to pay out of pocket for the second dose, which can be a barrier.

Kelly Cleland is the Executive Director of the American Society for Emergency Contraception (ASEC), which promotes access to and information about EC in the United States. Kelly previously worked at the University of California, San Francisco and Planned Parenthood of New York City and got her MPA and MPH at Columbia University. Before all the serious stuff, Kelly spent her early 20s teaching English in the Czech Republic and Vietnam and wandering around the world. Nowadays, Kelly and her family are passionate rescuers of retired racing Greyhounds, so their house is often full of tall, skinny dogs who like to nap.
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