Measured small, but had big baby?

[Alaura5]

I consistently measured ( with a tape measure, never ultrasound) 2-3 weeks behind from about 35 weeks on, and actually there was no change for the last 2-3 weeks and I think the largest measurement was about 36-37. My son was born at 41+2 and weighed 8lb 6oz. I'm also tall, though (5'10") so that might have made a difference.