When I went for my 25 week appt i was measuring 26, he said anything within 1 or 2 cm is normal juat as the other ladies have said!
I measured 4 weeks ahead for a very long time now I am measuring 2 weeks behind. My Dr has ordered ultrasounds and everything is perfect so nothing to worry about.
as long as your measurments arent "way off" you are fine. Every doctor measures diffrently and babies dont always grow at the same rate. You could also be carrying more toward your back or just be a smaller woman to begin with. Next week baby could have a growth spurt and your tummy might measure 36, try not to worry, its just a guess, as long as your belly is growing all is good. Also once baby drops you will notice it when measured:~)
I wouldn't worry too much about it, when I went in for my 25th week check up I ended up measuring 27" from pubic bone to the top of my uterus, I asked my Dr if that was bad and he said no not to be worried about it, that I was measuring right on track, so anywhere from 1-2" off is normal =0)
It's normal to measure at least a week or two behind or ahead.