Big Baby ! Tiny Mom

Had an ultrasound at 28weeks and 5 days, baby was weighing 3 lbs 9 oz. His head is measuring in the 97% and his abdomen in the 90%. I have another ultrasound scheduled for 33 weeks to see if he has evened out and dropped below 90%. Doctors say that anything over 90% they worry about and me being a petite girl makes it worse. I'm 4'10 and 100 pounds before this pregnancy. Does this mean I will most likely be having a big baby ? Has anyone experienced this and had to have a cesarean or did they have to induce early and let you push ? I'm a first time mom and don't know what to expect.