Brain Death: The Marlise Munoz Case

I am sure you have heard of the situation of Marlise Munoz in Ft. Worth who was brain dead, but the hospital kept her alive since she was pregnant.
My questions are:
What is the halachic position on this?
Can a body be kept on life support to keep a fetus alive?
Is there a point in the life of the fetus when the body must be kept alive (anywhere from 2 weeks of the first sign of pregnancy to term at 38 weeks)?
Can the family intervene and at what point does one party overrule the other: hospital, family, legislature, or the deceased person’s medical power of authority?