A few years ago, a group of researchers in the United Kingdom looked back on a study they had done about access to emergency contraception to see what they could learn about which women were most likely to become pregnant after using it. What they found, that emergency contraception seemed less likely to work for women with a BMI above 26, was a big surprise. Since then, this information has been all over the media, including most recently in Hulu’s show Shrill.

We asked Dr. Alison Edelman, an ob-gyn who specializes in contraception and family planning at the OHSU Center for Women’s Health, to help us understand what’s going on – and what women with high BMIs who need emergency contraception should do.

According to Dr. Edelman, while the study done in the United Kingdom identified BMI as a risk factor for failure, this type of study can’t prove that BMI caused the failure. “The study wasn’t focused on enrolling women of different weight categories, so we can’t know for sure. But we are definitely concerned that the most common type of emergency contraception may not work for women with higher BMIs,” she says.

What are the types of emergency contraception?

• Levonorgestrel – This is the active ingredient in the most common types of emergency contraception, including Plan B and Next Choice. Available in pill form, these options are easy to access over the counter, without a prescription, in almost any pharmacy.
• Ulipristal acetate – This is the active ingredient in Ella, another type of emergency contraception. For this one, you need a prescription, and some pharmacies do not have it readily available.
• Copper IUD – The same IUD that many women use for non-hormonal contraception is also the most effective method of emergency contraception. Getting an IUD requires an appointment with a doctor or other provider, and a short procedure to insert it.

"The study showed that levonorgestrel is the most likely of the options to fail for women with a higher BMI," says Dr. Edelman. "We’ve studied the type of progestin in this emergency contraception and we know that it is sensitive to weight and BMI."

For ulipristal acetate, the results of the study were less clear. It may also be impacted by weight, but not to the same extent, and is likely a better option for women with higher BMI. However, “Ella can be harder to access,” Dr. Edelman says. “You need a prescription, it’s often more expensive, and you may have to wait 24 hours for your pharmacy to get it for you as some don’t keep it in stock.”

We know that the sooner you take emergency contraception, the more likely it is to work – those 24 hours matter. 

What’s the best bet?

The copper IUD is by far the most effective option, no matter your body weight, and it will keep working as a contraceptive for as long as you keep it, up to 12 years.

“We know that some people don’t want an IUD, though, and getting an appointment quickly can be difficult,” says Dr. Edelman. 

That’s why it’s so important to find more easy-access options, like the emergency contraceptive pills, that work well for all women. Dr. Edelman and her team are conducting research to do just that.

The latest research

Dr. Edelman first set out to learn if the problem with levonorgestrel was that the drug levels weren’t high enough in people with higher BMIs and if those levels could be increased with higher doses. Many of her colleagues were predicting that doubling the dose for these women could solve the problem, but Dr. Edelman wasn’t so sure.

“Doubling the dose doesn’t necessarily mean that your body will see double the dose,” she says. “Drugs go through our system along a variety of pathways and we metabolize different drugs in different ways, so it’s usually not that simple.”

But Dr. Edelman was completely surprised by her results. Study participants with higher BMIs had 50 percent lower drug levels than other women. Not only that, but doubling the dose of levonorgestrel actually did normalize drug levels for these women.

They published the results and it caused quite a stir. Many people were thinking the problem was solved; they just needed to prescribe a double dose for women with higher BMIs.

“It’s really exciting, but it’s not something we can recommend in the clinic yet,” says Dr. Edelman. “All we know is that a double dose means enough drug reaches the blood stream. But we only did this in five people and we didn’t look to see if their ovaries responded in the same way.”

Moreover, Dr. Edelman is concerned about the cost. After all, it’s not really fair for some women to have to pay twice as much for the same result.

Based on the results, Dr. Edelman is now enrolling for another study looking at the ovaries of women with higher BMIs who have taken both single and double doses of levonorgestrel. 

“It’s a fun study, because you get to see yourself ovulate, and levonorgestrel emergency contraception is really well tolerated,” says Dr. Edelman. 

Prevention is key

With all this talk about emergency contraception, it’s easy to forget that preventing pregnancy is easiest and most effective before you have sex. Long-acting birth control methods, like implants or IUDs, are incredibly effective. And short-acting methods like pills, patches and rings, appear to prevent pregnancy similarly for all women, no matter their weight or BMI, as long as they’re taken consistently.