WOMEN
01/24/2014 04:36 pm ET Updated Jan 24, 2014

Europe Reviewing Morning-After Pills: Are They Less Effective In Women Over 165 Pounds?

Martin Barraud via Getty Images

Are emergency contraceptives really less effective in heavier women?

In November, French pharmaceutical company HRA Pharma announced that it was adding warning labels to its popular morning-after pill, Norlevo, after studies found the drug was less effective in women weighing more than 75 kilograms (165 pounds) and that it didn't work at all for women over 80 kilograms (176 pounds).

The European Medicines Agency (EMA) announced this week that it is currently reviewing morning-after pills to check the veracity of this claim.

"This is an efficacy issue," said agency spokesperson Monika Benstetter, per The Associated Press, adding that the EMA -- an agency of the European Union -- would be performing an assessment of all EU products in the same category as Norlevo to check for consistency and to find out if there is indeed "a cut-off threshold for when the medicine becomes less effective."

Mother Jones wrote in a post last year that Norlevo, which contains the active ingredient levonorgestrel, has the same chemical structure and dosage as some American emergency contraceptive pills including Plan B One-Step, Next Choice One Dose and My Way.

According to the AP, a number of European brands -- ellaOne, Levonnelle and Levodonna, among others -- also contain levonorgestrel.

Since the average weight of American women aged 20-29 is 161 pounds (just 5 pounds under the weight at which Norlevo becomes less effective) and the average weight of an American woman aged 30-39 is 169 pounds, the EMA review and other developments surrounding this issue certainly have implications for women in the United States. The U.S. Food and Drug Administration has also said it will look into the matter.

According to the Centers for Disease Control, approximately 11 percent of sexually experienced American women between the ages of 15 and 44 used emergency contraceptives between 2006 and 2010.

"There's no evidence that similar warnings will be popping up here [in the U.S.], but our version [the Plan B pill] is formulated with similar levels of the same kind of synthetic hormones as Norlevo," wrote Slate last year, "meaning there's every reason to believe that women who weigh more than 165 pounds in the U.S. are just as prone to see a decrease in the pill's effectiveness."

EARLIER ON HUFFPOST:

CONVERSATIONS