On the size thing, in my induction article a midwife shares this story:

“... I was involved in a birth a few weeks ago where the woman was induced because of previous macrosomic (big for dates) baby. She had gestational diabetes with that pregnancy and previous shoulder dystocia (first baby, this was her 3rd). We attempted induction at 36 weeks and it failed. Induction was again attempted at 37 weeks which was successful – baby was only 2750g – hardly macrosomic! The ultrasound had estimated a baby weighing 3500g so it wasn’t even close. I think if she had that baby at the first induction attempt at 36 weeks it would have had to go into Special Care as it would have been under 2500g which is our cut off. Frightening.”