Fire Fly... I read this last night and thought it was interesting:

Ultrasound weight estimates followed by induction for suspected large baby increases the risk of caesarean without improving outcomes.
Ultrasound diagnosis of macrosomia (large babies) also hurts rather than helps. Five studies found that ultrasound predictions that the baby would be macrosomic were wrong one-third to one-half of the time. In addition, two studies looked at the effect of ultrasound diagnosis on macrosomia on outcomes. Both found that when the obstetrician believed, based on ultrasound, that women were carrying macrosomic babies, half had c-sections versus less than one-third of women not thought to have macrosomic babies who actually did.
Got it from "The Thinking Woman's Guide to a Better Birth".