I’ve always been torn on this choice. The baby doesn’t have any history, and frankly, you can always make another. But on the other hand the old lady has already lived most all of her life (well all of her life depending on this decision). I mean there isn’t a good answer unless you try to go for a two’fer

…getting ready for the impact. And I don't know if I can do it…

And it's done as a console game choice - you have to pump X or O fast enough, otherwise you kill them both