I've already read about this question/scenario.
Given that all of us, that means, the baby too, will be killed immediately in case we are found, it is not a situation where I have to weigh up lives - it's the baby, or the baby plus all the others. So, the right thing to do would be to kill the baby.
But the question was if I was actually capable of smothering the baby. I have only once been in a live threatening situation before, so I think I can hardly imagine what people in such a situation feel like. I would certainly hope for somebody else to do it. But if I'd come to understand in the end that nobody else is going to do it, maybe I would be capable, yes. The fact that the parents are not around sure would "help". A possible punishment would not influence me, since I'm aware of the fact that I would in any case have to deal with my deed for the rest of my life.