These are all good points. Has anyone recently played the part of the ritual with TerraEx's dialogue patch installed? I am on a character now to reach that point, but will take me a while. I wonder if there is dialogue restored there that might shed some light on the nature of the baby and the Ritual itself.
Sadly the ritual scene itself was the most compromised part of the final game. Gaider stated there were supposed to be ritual variant scenes for a romancing & friendly warden that had specific dialogue for those who romanced her/befriended her. These got cut - completely, so we get a one size fits all Dark Ritual. Heck, he also mentioned there was supposed to be at least some element of magic involved as well, but this was apparently too taxing for them to add as well.
I did restore I think one branch of dialogue to the ritual, which allows you to ask her why she never mentioned it earlier iirc as well as fixing bugs where a female warden could do the ritual herself

But sadly, there's nothing more to work with in the Dark Ritual scene - it was cut down & no great revelations are hidden in the dialogue... The closest thing you can hope for is the comic that Gaider & Aimo collaborated on, which attempted to show a softer, more caring side to Morrigan, undoubtedly a scene that was planned for the game.-
http://blog.bioware....velation-comic/So yeah, its the one scene in the game where those who romanced her were expecting some kind of recognition for their efforts, but we get naught but disappointment unfortunately. People have speculated that she's out of character in the ritual scene, or that she's been possessed by Flemeth etc, the common consensus on the Morrigan thread over on the bioware forums is that the ritual scene was essentially hacked together to compensate for said cuts, hence her demeanor toward the warden throughout the scene. Based on Gaider's comments in the above comic, its the logical assumption. With regards to the baby itself though, its obviously a plot hammer moment to be used in a potential sequel and the choices you have available don't allow you to ask any meaningful questions. It's accepted that Flemeth will return for example, then how does it make sense for Morrigan to say, "yep I'm going off solo, don't follow me..." while the threat of Flemeth remains. Surely it would be a smarter idea to allow the warden to stick around considering he's already taken her down once before.
Whatever the case, the Flemeth/Morrigan plot thread is one of the main reasons I'd like to reprise my role as the warden in DA2, but that's a whole other rant and I've bored you enough already