Oh wow, I did not think of that!Actually, that's not the full formula - as Vastra said, all the circumstances of River's conception did was give the Church "a hell of a head start" - the Church still had to do a lot of genetic tinkering (she's stated to be mostly human but have some Time Lord DNA which wouldn't have come from the Vortex... the disturbing implication is that the Church have samples of the Doctor...).