Instead, what may have happened are situations changed for the couple. Maybe a nasty divorce occurred, or one of the partners abruptly left the relationship for reasons? Or maybe the father suddenly died? Or lost his job (or she did - or they both did)? Or any one of those coupled with already having other children. Any one of those, and other reasons, could be the case. Had something like that happened late in the pregnancy, where a legal late-term abortion wasn't available or allowed, then adoption might be the only choice for the parent(s).
That doesn't mean s/he wasn't wanted by the birth parents, but that they instead (perhaps) loved the resulting infant so much that they decided adoption would give a better chance for life than keeping him/her. Maybe that was the wrong choice, maybe not.
Adult choices are rarely easy.
Your birth parents may not have wanted you, putting you for adoption. However, you were wanted in a different sense, chosen for adoption by whomever adopted you.
-shrugs- Don't know what point I wanted to make, just a thought