Many women carry extra fluid during pg - this is often quite normal and I am dissapointed in your Ob for suggesting to induce you if bubs proves to be large at your ultrasound - just look at the concern it is causing you already. There have been numerous studies to prove that there is absolutely no benefit to induction for a suspected large baby and induction in itself brings about its own set of risks - including c/s. Ultrasound is also NOT the best indicator of babys size, they are notorious for getting it wrong and it does nothing but worry the mother.

Other factors may still be playing a part in why you are measuring ahead - the length of the baby (you could have a really long, but average weight baby), the position (even though bubs is head down they can still be high) or there could be no reason at all - some women do just get 'big' during pg and go on to have average or small babies. You may even find that once baby engages that the fundal height will either drop or stay the same.

Either way, what does it matter if the baby is large - you are designed to have a baby that is the right size for you to birth vaginally and that includes the large babies. Women need to let go of the fear of birthing large babies - it can be done.