[Aristophanes]

I remember reading that the move to change the definition of "conception" to require implantation began as early as 1963 when certain pro-contraception members of the AMA wanted to smooth the way for the birth control pill -- which they realized even then was an abortifacient.

Sorry I don't (yet) have a reference to this. I'll try to find one tomorrow.

[MHGinTN]

If it will help your search, Aristophanes, the doctors were working with/for Searle Labs; Searle brought the first contraceptive pill (as a birth control pill) to market in the U.S. I believe Ortho Pharmaceuticals was next with Ovicon,