Huy, don't worry mamsh, one week difference is totally normal at yan talaga ang dating ng ultrasound measurements, hindi sila always exact sa counting! A few of us tried calculating based on dates and then the u/s shows something different, kasi may margin of error talaga especially in early pregnancy, at every baby develops slightly different din. Since your OB didn't mention anything during the scan mismo, siguro okay lang ang baby mo, but definitely ask your doctor about this sa next checkup mo para maging at ease ka completely, they can explain kung bakit may slight difference at make sure everything's progressing well, okay? Breathe, first pregnancy kaya madaming overthinking, yan talaga normal sa atin moms!