While working in pedatric endocrinology I saw a lot of things.
The first thing I saw was people desperate to save their 6-10 year olds. I understand that completely. Their child often had cancer and most days was perfectly healthy, but was progressively spiraling downward. I had to eventually leave the practice because it was heartbreaking.
The second thing I saw was children who were "heroically rescued" at birth and were suffering their entire lives. Their parents had made the choice for them (the burden of parenthood to be sure) and had them saved. These kids were miserable. Most couldn't even attend school for the requirement of constant medical attention, and many of them will never have jobs.
This is not a statement on people with disabilities not being able to be productive members of society in any way. The financial burden that their parent's incur on their behalf does a few things: stresses the parents out, stresses the child out, causes healthcare costs to go up.
Being born prematurely and being born extremely prematurely are two very different things. A premature baby that is small, but has a chance as a normal life with medical help needs to be saved. Absoultely 100% needs to be helped. A child that has no chance at enjoying life's simple pleasures, why are you doing that to the kid?
If you're religious you may believe their soul will be reborn into another body, a healthy body. If not, you may believe this person simply fades, either way, forcing someone to live and never enjoy life is torture.
Ultimately the decision is up to the parent, and it should be respected. But people need to be aware when they make decisions to force someone to live, be it a premature baby or an individual who is between life and death in limbo, you are affecting someone besides yourself. Your sorrow over losing that individual is nothing in comparison to the feelings of that individual about the situation.
Are you truly giving them the best life, or are you just afraid to make the hardest decision of your life?