One of the things the scan will be looking is to see how the blood flow of the placenta is going. Sometimes the placenta doesn't function as well towards the end of the pregnancy and then the baby doesn't grow as much. It might then be termed a IUGR (Inter uterine growth restricted) baby. If that is the case they might start discussing induction with you as apparently it is easier to feed them up on the outside than the inside. Doesn't mean there will be anything wrong with the baby at all they will just be smaller and require feeding more often as a newborn.

Good luck!