In a brief to the Supreme Court last October,
the American College of Obstetricians and Gynecologists and 10 other health professional associations make that assertion.
The label hasn't been updated "since the product was originally approved in 1999," the brief says, "and it does not reflect the most current research."
The brief further says that the hormone in Plan B has been widely studied and "current evidence shows that[ it works by preventing or disrupting ovulation, but is not effective after ovulation."
Teva Pharmaceuticals, Plan B's manufacturer, is well aware of the problem with its label.