Effectiveness of Emergency Contraception for Overweight Women Reviewed in Europe

New data prompts drug agency to investigate how weight affects several contraceptive brands

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The European Medicines Agency (EMA) — the European version of the U.S. Food and Drug Administration (FDA) — launched a broad review of whether body weight influences the ability of emergency contraceptives to prevent unintended pregnancies.

The agency recently required makers of the European version of Plan B, called Norlevo, to add an alert that the product may be less effective for overweight women. The move was spurred by a 2011 study that found that women with a body mass index (BMI) greater than 25 who used levonorgestrel, which prevents pregnancy by blocking the release of the egg from the ovary, inhibiting fertilization or changing the uterine lining to discourage pregnancy, were four times more likely to get pregnant than women with lower BMIs.

MORE: Europeans Warn Plan B Is Not Effective in Heavier Women: 5 Things You Need to Know

Now, based on that study and other data, the EMA is turning its attention to other emergency contraceptive measures that rely on hormones to prevent pregnancy. These include Norlevo, Levonelle/Postinor and Levodonna which all contain the hormone levonorgestrel. All the medications are available over the counter, and the agency is also studying one prescription-based medication called ellaOne that includes ulipristal acetate.

It’s unclear why emergency contraception could be less effective in overweight women, but the U.S. FDA is also reviewing existing data to determine if any changes in labeling or action is necessary. Calls to the FDA were not immediately returned.

Reproductive health experts say women who are concerned about whether their emergency contraceptive will prevent pregnancy should consider other birth control methods known to be more effective, like the IUD.