My OB says it depends on your body pre pregnancy and how you're carrying. I'm not that big, smaller than a girl at work who's 3 weeks behind me, only gained 12 lbs at 30 weeks but baby measures big. Lol. Crazy.
I'm so glad to see other ladies with belly's measuring small giving birth to completely normal sized babies! I am not worried at all, but my OB's keep acting like it's a huge deal at the last couple scan's saying my belly is measuring too small, even though at my scan at 29w she was measuring in the 57th percentile. I have a scan scheduled for tomorrow (they've been monitoring my SCH) and so the OB's are insisting on a growth scan while I'm there to be sure baby is 'ok'. It really surprises me that they are being so worrisome over something that seems to be as inaccurate as a belly measurement. lol