Yes, keeping the pregnancy, especially when Steph was exploring her other side as a teenage vigilante, always seemed... not too well thought out.
I figure we've probably got at least another 5-10 years before Stephling shows up as a teenage vigilante. Turning up any earlier is likely to be a kidnapping, either because the adoptive parents are just not boring enough, a random event occurs, or someone twigs to the fact the kid's a Brown.
I'm waiting for the kidnap/missing persons report that sends Tim into a wild hunting frenzy, actually. Especially as every other Bat will be going Bzuh? about why Tim's so into this case (Except maybe Babs). Because the chances of Tim being oblivious to the kid's whereabouts is about the same as Bruce not knowing where Helena ended up. Between Tim's 'everyone dies!' issues and his thing about parents, he probably checks in on the kid at regular, random intervals. From a tree, with binoculars.
I hold out hope that Bruce's answer to the shell game they played, hiding Helena, was simply to track every kid placed by the three agencies who's within a few months of Helena's age. But he probably still knew exactly who had her.