I want to say good luck to you in what you decide to do. I love my dogs so much and I know it would be devastating to hear this news. But I would really think about it, at 12 years old a dog is old and maybe not worth making your baby suffer through heart conditions or cancer. I don't know I may feel different about it then others but it could be very costly to treat and you can't guarantee an outcome. I will have you and your baby in my prayers