Anatomy Scan- need to return

I had my anatomy scan today at 19 weeks 5 days and we went from everything looked perfect to me needing to come back because his head measured large. The doctor initially said everything looked great then I asked if they took the heart rate and when she did another glance she mentioned his head being on the larger side and to come back in 6 weeks. My first son had a large head and I told her that but she wants me to come back. The tech didn’t seem alarmed by his head size at all. He was measuring over a week ahead anyways and was already at 13 oz. Any thoughts on this? Anyone experience something similar?