Loss of unborn niece/nephew

Thought I would share my story, maybe I can get some sense out of it.
My sister was 5 months pregnant, and a couple of days ago went for a routine scan, they found out the baby had died. We are extremely close, and went trough a lot together: brain cancer, death of a parent...
She is devastated, and I don’t know how to make it better. It’s her first child, and we had so many plans... I never seen her so down. I hurt for her and my brother-in-law and I hurt for me. Can’t even describe what I’m feeling. I just don’t understand.