My son was average size right up until about 37 weeks, I went to see my ob and he was amazed at how much weight he'd put on in about a week. As a result I was induced at 38 weeks and had an agonizing 20 hour labour, with every intervention under the sun. He was a vacuum extraction and had shoulder dysplasia, and due to the extensive bruising he suffered he was under lights for a few days. I had about 40 stitches. I should have had a caesarean, all the midwifes were disgusted that my doctor had put me through this. This was a private hospital as well!

He was 10lb 4oz at birth and 58cm long so would have been well over 11lb if I'd gone to full term. I don't know if I would have had a better birth experience if I had been allowed to go into labour naturally. I suspect so, but due to his size (especially his monstrous head!) he took such a long time to get through my pelvis.

It's true that body size doesn't seem to have much impact on how easy babies are birthed, I'm tall and quite a big woman, my sister in law is tiny and she had three babies, one in my mother in law's bathroom when she didnt make it to the hospital in time! her longest labour was about 2 and 1/2 hours.