To provide the background: I am playing Dragon Age: Origins a computer game where your decisions affect the environment around you. In this case one is sent on a quest where a demon has possessed a child. You have two options.
Kill the child and thus kill the demon.
Use Blood Magic - something that is blasphemous - sacrifice the mother and enter the demon world to kill the demon and let the child live.
Now is would not be a realistic case in our modern world. But if the question arose where you were placed in a situation where you were forced to decide between killing a child or killing his/her mother, what would you choose?
Essentially killing one will allow the other to live and you have no idea what the future holds.