Its all guess work really & like Cherie I agree... an experienced hand is best.

My u/s 2 days before my baby was born measured her at 11lb. She was 8lg 13oz... HUGE difference. She is/was very tall and since they only measure the bone length & head circumferance to find the weight, its never going to be spot on anyway. The OB who felt her 3 days before the birth said she felt like a 4kg baby...she was 4kg spot on.