The second, third, and fourth time I put the babies in the inventory manually (I picked them up and hit backspace). I think it's something that you're supposed to be able to do actually (to prevent you from losning the baby when bulldozing a lot or downloading a new house from the gallery), though if you try to leave build mode with a baby in the inventory the game won't let you and a pop-up explains that you need to take the baby out of the inventory before returning to live mode.
Hm so it's basically a temp storage thing for when you're building.
I'll add this
That's what I figured at least. The game treats the baby more like an object than a sim so it can't push the baby off the lot during renovations like it can other sims, the game needs to be able to put the baby in the inventory or it could be lost forever when the player does things like bulldozing the lot.
And the player being able to put the baby in the inventory is just convenient. You can just put it in there and not worry about it being in the way while building.
I did another test and the first thing I noticed was when you pick up the basin with the baby in build mode there isn't actually an option on screen to put it in the inventory. So maybe I was wrong and you're not actually supposed to be able to put babies in there and it's just a glitch that you can do it with backspace. Anyway, this time I had the baby stuck on fine and after about half a day I was warned about the baby starving, but then nothing more happened. I watched the baby for two in game days, but it didn't disappear and I didn't get any more warnings, and as far as I could tell the other sims in the household ignored the baby completely. I probably should have tried to watch it a bit loner, but I'm tired and not really in the mood right now.
