Baby girl measuring 5 days small.

Had anatomy scan today and she’s 5 days smaller then my dates. I’m 20+5 she’s at 20. My son who’s now 12 months was already over a pound at this stage. She’s at 12oz.

I know all babies are different but is this something to be concerned about I feel like I’m going to worry all weekend that the dr is gonna call Monday. Blehhhh