They may want to induce you early because of it, but there is no real evidence to support this other than trying to avoid a larger baby. You will not be 'allowed' to birth at a birth centre or similar because you will immediately be classed as high risk. There is a really good article on here by Henci Goer about gestational diabetes being a diagnosis in search of a disease and it's really good. Michael Odent has written about it too.