From that description, I suspect you're referring to RU-486 (the "morning after pill"), rather than "the pill" (which, unless I'm mistaken, prevents conception altogether).
You are confused. RU-486 is a "medicine" given in combination with another to cause severe cramping and expulsion of the uterine contents. A woman visit the doctor for these "medicines" and then goes home to cramp up and expel her fetus into her own toilet. It is a "private" alternative to the typical early term "surgical" abortion.
The "morning after pill" is nothing more than a high dose of regular birth control pills. A woman who is on "the pill" and has sufficient knowledge can give herself the "morning after" treatment by double dosing on the pills she already has in her possession.
Why does this work? Because the normal birth control pill is not merely a "contraceptive." One of its methods of working is to inhibit the normal function of the ovaries, preventing the release of an egg during the woman's regular cycle.
But, if you manage to slip one past the goalie, the pill also works to make the uterine lining inhospitable to attachment of the fertilized egg.
Were it not for the "medicine" the woman was taking, the fertilized egg would take root. The "medicine," therefore is responsible for the demise of the fertilized egg. This is no different, morally, than any other abortion procedure, whereby an "unwanted" "product-of-conception" is disposed of.
SD
Funny. I guess I'm not the only one who is, in your not-so-humble opinion, "confused."