I can give you a reassuring story. My son was missed completely, and was only diagnosed as a 4 year old. The specialists who saw him were fascinated at the shape of his head (completely oval, with a double-depth bone on top, and a distinct long back of the head) and were concerned he might have some sort of brain damage. It was too late to operate so they followed him up for the next ten years.
He was peculiar looking as a child. He was teased about it. But as he grew it sort of normalised and he is now a fantastic young man, very intelligent and very handsome (not just me saying it, he's was top of the class at primary school and has done a lot of modelling as a young adult!).
I'm glad, with hindsight, that his diagnosis was missed and I didn't have to decide about, and go through with, operations and helmets. But then his was symmetrical, the fusion was straight down the middle of his head, so we didn't have to deal with some of the issues other children have to go through.
This is a condition that has been thoroughly researched. Specialists in the area are very used to dealing with the most extreme conditions, and as far as I can see all the children (operated on or not) come out of it pretty well. I second the suggestion of not googling - you come up with two sets of results. The very extreme (which, if your baby had it, would have been diagnosed at birth if not before) and the ultra-worried-over-insured-American sites who want an operation for every child who doesn't have a perfect head.
Neither is helpful!