Pregnancy question.....what would you do??

ok here is the situation..my pregnancy is very rough now, and i am on bed rest and i was wondering if you can give me some input on this situation...as of right now i am 3 weeks shy of 6 months, and my baby is not moving and her heart beat is very very weak, and the dr said that she may not make it...he said that she has a weak heart and i may not make it to 6 months cuz her health is slowly deteriating.(spelling sorry) and he said that i should terminate the pregnancy before it would put my life in jeopardy to...WHAT WOULD YOU DO???? and i do have an option to have it early at 6 months but i have a 50/50 chance of her not being alive...or even worse still born...PLEASE HELP....WHAT WOULD CAUSE HER HEART TO DO THIS AND MY PREGNANCY NOT TO BE HEALTHY???? IM SO UPSET....AND ITS A GIRL BTW..BUT THANX FOR READING......