Elective gender scans...

I'm getting one Saturday and I'm super excited! I've had ultrasounds in the ER twice and the baby is definitely growing but I havnt had it actually measured since 11 weeks! And at 11w and the one before at 9w the baby measured a few days behind.... I just wanted to see if they normally measure the baby for you while your getting the elective or what? I want to see if baby has caught up!!