Dr ordered another ultrasound

Mariah
I just went in for my regular dr appt. instead of the fundal height measurement being on track at 26 it was 29. Everything's has been normal and following everything by the book. So my dr ordered another ultrasound to check my fluid levels. My glucose test came back great so I'm not worried about gestational diabetes.
I'm hoping she has just grown a lot, but I'm still worried. 
Any insight? 
Due June 27th.