Inside Emergency Contraception for Every Campus, the birth control distribution network - Washington Post

To be clear: The morning-after pill works as a contraceptive because it releases a flood of hormones that staves off ovulation. Without ovulation, fertilization cannot occur. Plan B almost certainly does not — counter to some outdated label information that advocates have begged the Food and Drug Administration to correct — prevent the attachment of a fertilized egg to the uterus...

https://www.washingtonpost.com/magazine/interactive/2022/birth-control-distribution-ec4ec/