ultrasound techs?

Merisa

Hey so I had a vaginal ultra sound done with my son when I found out I was 1st pregnant at 8 weeks and then also to confirm my 2nd pregancy I had an abdominal ultra sound. the size of my son at 8 weekswhich was 1st pregancy is smaller then my ultrasound now which was at 6 weeks. it is possible the tech measured wrong