Second percentile small baby

Has anyone been told at their 20 week anatomy scan ( mine was at 19 weeks) and she was measuring a week behind, at my next growth scan she was still small and was still a week to two weeks behind but still growing. However she's small and they said she's in the second percentile but still growing and everything else looked fine. Did anyone else have this and everything turn out to be just fine? The high risk doctor didn't seem to be worried but stated I'd have to have another scan he just said he wasnt sure as to why that she could just be small. Worst case scenario delivering early. But did anyone else go through it?