Honestly? I would find a new OB. Failing that I would ask them what the variance is in the estimate. My understanding is that the tolerance for these estimates is huge. I remember reading that estimates done via ultra sound can be + or - up to something like 40%.
ETA: Being induced early especially for a first time baby will drastically increase your chances of the birth ending in an emergency CS.
Sorry if I sound all negative, that's not my intention. Like all women about to give birth I just feel you should be armed with some information or at least questions to ask your health care providers.
Best of luck with everything.