Personally, I would smother my child. I would do this because I feel if I did not then I would be making decisions on everyone else's life in the room. The only ones who I have the right (in my opinion.. not in a legal sense) to decide life and death over are myself and my infant (and the infant ONLY because it can not make such decisions).
If I smothered my child and the enemy stormed in anyway and killed all of us, then I #1. wouldn't care anyway cuz I'd be dead and #2. would rather have had my child die at my own hands than be bayoneted to death or worse.
If I smothered my child and the enemy never found us, then I feel I would not have put other people in harm's way. If there are 15 other people in the room with me and my child's crying is sure to kill us all... but I can potentially save us by quieting it.. then I feel, personally, that I must do that. I can not, in essence, kill everyone else in the room.
So. That's my decision. But I am also not a mother.
When I thought about my kitty being in my arms instead of a baby (he's the closest thing I have to a kid and I love him dearly) I hesitated but... I know I would definitely quiet him in the end. Again, I am holding other peoples' lives in my hand. I would not allow myself to be part of their deaths.