Warning: Morning-after pill may not work for ladies over a certain weight

French researchers have found a morning-after pill, similar to ones sold in the US, can be less effective for women over 165 lbs..

A drug manufacturer in France has issued a warning about the effectiveness of the morning-after pill for women over 165 pounds.

The news is cause for concern, even for American woman, because the US Food and Drug Administration says it's now reviewing the issue.

HRA Pharma says the findings convinced them to change the labels on the drug in order to warn potential patients.

The drug, in question, is sold under the brand name Norlevo in Europe.

It is, however, similar to morning-after contraceptives sold in the United States under the brand name Plan B One Step and in generic versions under other names, according to Princeton University public health expert Kelly Cleland in a CNN interview.

According to the same CNN report

, HRA scientists discovered that its Norlevo began losing effectiveness in women who weigh about 165 pounds and was not at all effective in women weighing over 176 pounds.

The scientists were actually studying another issue when they saw that a woman's weight had an impact on the pills effectiveness.

(AP reporting contributed to this article)