Low amoid fluid and kidney problem

I am 20 weeks pregnant and found out that my baby son has a disease called Polycystic kindey disease.  He is developing with one kidney and has cysts all over it and it badly damage.  On top of this I have no amoid fluid.  This is my fourth pregnant however I only have 2 girls.  My first one was full term.  My second one was a boy and I deliver him my self at 21 weeks he lived for 4 hours and died.  I was told that I got an infection in my cervix and the baby detached from me.  My third one was a baby girl and she was preterm I had her at 26 weeks.  My fourth one is my son and he the one one with the disease. I have made the choice to stop prevention of having this baby early.  Since all doctor have told me hes going to die because of his lungs not developed.  So my question Am I doing the right thing?  Is there any one that have survived with born with this desease and not develpoed lungs?  I am scared to death I am making the wrong decsion?

[ku111]

Is the kidney disease in one or both kidneys?  Do they know why you have no fluid?  Is it no fluid or low fluid?  Sorry for all the questions.  Is it a high risk OBGYN that has told you this?  I am thinking of you and wishing you all the best.