Actually, from what I remember of the original storyline, there was a two-fold purpose in choosing Ashley as his target. Number one was her relationship to Victor, Number two was her relationship to Jack; Adam wanted to get back at/punish both Victor and Jack because of the whole stupid Diary Scandal, and tormenting Ashley was simply a means to an end. Adam simply saw Ashley as an effective tool to use in his war against Jack and Victor; he never hated her or her baby; he actually liked Ashley and was devastated when his ridiculous scheme went too far and resulted in Ashley falling down the stairs and losing the baby.
As far as the baby was concerned, I never got the impression that Adam wanted to eliminate it, in fact, he always came across as not giving two shits about it one way or the other. The target was always just Ashley, and that was because of her importance to the two men (Jack and Victor) who just screwed him over - at least that is how he saw it. Back then, MAB was writing Adam as a single-minded sociopath hell-bent on revenge. It has always been my belief that Chris Engen wanted out of the show because of the over-the-top, sick-ass storyline - and the whole Gay Scandal was simply manufactured by TIIC to make themselves look good to the viewers.