Abortion foes have long argued that morning-after pills like Ella can act as abortifacients, substances that cause abortion. These claims have been strongly debunked. Evidence shows that Ella, when taken at its standard 30-milligram dose, works by delaying ovulation, preventing fertilization.

The research could further complicate the polarized politics of abortion because the drug in the study is the key ingredient in a pill used for emergency contraception.