I wouldnt worry to much hun, how big are you measuring? With my first baby I was constantly 4-5cms bigger than dates from about 24 weeks on. It was never really an issue, they just prepared me to have a big baby, and he was. He was 8lb 14.5oz when born, which although large, is not excessive. I never had any extra growth scans or had to meet consultant, they just constantly measured to make sure it wasnt getting any bigger.
I dont think it becomes a major issue unless you are particularly small or baby starts measuring excessively big, in which case they might check for gestational diabetes and other growth conditions. But in any case, at worse case scenario if baby is bigger than they would like, they might just induce you early to get baby out before they grow too big. Its usually just a precautionary thing, and they are not always right, you might just have a tall baby! x