Would you refuse induction till 40 weeks under these circumstances?

[Listzilla]

I'm 35-3 and diabetic. My blood sugar has been well controlled, all my levels have been well within the normal range, using small doses of insulin.

I was induced last time at 38 weeks because my insulin requirements had increased massively since the start of the pregnancy. The baby was measuring perfectly normally though.

I had an appointment yesterday and the registrar said that because my control has been so good this time, they wouldn't induce me till 40 weeks (they never let diabetics go overdue).

Then she did a scan and said that the baby was measuring on the big side - he looks to be about 6lbs 8 now, and going by the half-a-pound-a-week thing, he'd be about 9lbs at 40 weeks. She referred me for a more detailed scan, and said that if he's confirmed to be the size she thinks he is, they'll induce early after all.

I don't think 9lbs is that much of a whopper really; my family and DH's all have big babies (my dad was 14lb 8oz!) and it hasn't caused any of us problems. DD was 8lbs 2oz and the birth was very straightforward and the recovery very fast. If induction is being suggested purely for size reasons, I'd rather wait till 40 weeks and see if I go naturally.

Am I mad?

I'd tend to go with what I'm advised medically speaking. With the exception of the HV when I tend to listen to Mumsnet :)

It does sound like your getting great care and I'm sure they'll monitor you lots if you do delay induction. Do you need to make a decision now though? Maybe just say you'd like to wait till 38 weeks before you make the decision.

I was supposed to be induced at 38w (for OC) but my bloodwork started looking better so pushed back to 40w and I went naturally at 39w so it does happen.

It's difficult, because those late sizing scans have a wide margin of error - 10% or more I think, which at 9 pounds is almost a pound either way. If I were you I would ask at the next scan what their margin of error is and then you can calculate whether you'd be happy to deliver a baby within that range (e.g 8-10lb).
If you've already delivered an 8lb+ baby easily then there's no reason to think you shouldn't deliver a 9lb one especially as most people find it easier 2nd time round.
Additionally some of the things that happen during an induction (being strapped on your back for example) may reduce the pelvic outlet and make delivery of a bigger baby harder. So you might have an easier delivery of a 9lber if you had less intervention (e.g. hands/knees position, in water etc).
It sounds like induction worked out well for you last time. I guess you really need to find an HCP who will properly discuss risks/benefits with you so you feel confident in your decision.