New study: BMI affects contraceptive use

A woman’s BMI and weight can affect the way that emergency contraception, specifically the Plan B morning-after pill, works, according to recent studies.

Plan B becomes significantly less effective for women whose body mass is over 25 or body weight over 165 lbs, according to experts Judy Klein and Kathryn Brown from the IU Health Center, For women over 176 lbs, Plan B loses effectiveness completely.

Klein, a physician at the IU Health Center, defined BMI as “a way of trying to look at weight appropriateness for height.” She cited a healthy BMI as between 18 and 25.

The solution for overweight women, Klein said, is a morning-after pill with a different mechanism of action. Plan B contains progestin only. However, medicine with a different chemical makeup, such as the emergency contraceptive Ella, is better for larger women.

“We don’t know why, except that different chemicals are metabolized differently and weight can influence how drugs are metabolized,” Klein said.  

Klein said that at this point, she can only guess why progestin-only emergency contraceptives are not as effective for women with a higher BMI.

“It probably has to do with changes in the liver, which is responsible for breaking down or metabolizing medications as people become heavier,” Klein said. “But no one really knows.”

Although this study was published in 2011, companies have only now started to take note, Klein said. European manufacturers just started publishing warning labels about the decrease in effectiveness based on a woman’s weight.

Klein said that the FDA has not yet changed any warnings or labels on American emergency contraceptive packaging. However, she said it is information that users cannot ignore.

“The fact is, we now have this information,” Klein said. “Regardless of what the FDA does, there is this study that we need to pay attention to.”

Brown, an IU Health and Sexuality educator, said that the IU Health Clinic first became aware of this study in December 2013 and immediately discussed getting the word out to their patients.

According to a Center for Disease Control study that used data from 2006 to 2010, women aged 20–24 were most likely to have used emergency contraception.  About 23% of women said they had.

Plan B and Ella are both available at the IU Health Center’s pharmacy.

Klein said that although students need to factor in their BMI to the equation now, the

IU Health Center continues to recommend the morning-after pill in the cases of unprotected sex.

“There will always be a need because condoms break,” Klein said.

Klein recommends a “highly effective contraceptive method” and condom use to every sexually active student.

According to Brown, the most effective birth control available currently is an IUD.

Although IUDs are initially pricier options, the Affordable Care Act, prescription birth control is free to women with health insurance, and Brown said that she encouraged patients to take advantage of this.

For cases of unprotected intercourse or a malfunction in a condom, both doctors said that an emergency contraceptive is the right step.  

“Emergency contraceptives will always be needed and with these circumstances, the new reality is that we will have to look at the weight issue and give the best advice about what would be most effective,” Klein said.