One soft marker found at 34 week scan

Just need advice please. I had a NIPT done around 12 weeks and it came back negative. I had a growth scan a week ago and apparently they found one soft marker on my little girls brain. My OBGYN told me not to be concerned because she isn’t but I literally cannot help but to be. Has ANYONE gone thru this? She said the only reason she would be concerned would be if there were more than one markers found and I had a positive NIPT, but that’s not the case.