I am also a STM who had a scheduled C with DD owing to macrosomia -- she ended up being a BIG 10 lbs 9 oz with a large head.
With this one, I am again measuring big -- my fundal at 36 weeks was 40. I went for an U/S about a week ago, and baby was at 8 pounds, with an estimated 40-week weight of about 9.5 pounds.
HOWEVER, doc then said that the bigger the baby, the more room for error in the U/S estimate and that based on my fundal and just how I look, he thinks more like 10 pounds or slightly more.
My fluid level was OK -- at least, they didn't say anything to the contrary.
So I am wondering if maybe your estimate is just off. How big was your first baby in the end?