Head measuring 3 days behind

I had my anatomy scan at 21 weeks 6 days. The tech wasn't able to get all the images needed due to baby not moving enough but baby's head measured 21 weeks 3 days. My doc said she's not concerned and will have me back in 4 weeks for another anatomy scan to get the rest of the images needed but I'm a little worried after googling and wishing I didn't have to wait 4 weeks. Have you Mama's experienced this and was baby okay?