ultrasound question

Okay, so here's the deal: I pay out of pocket for ultrasounds and, last week, my doctor told me that the baby seemed to be measuring small and said she wasn't worried about it, but wanted to do an ultrasound to check on the baby after a week. So my ultrasound is scheduled tomorrow and, like an idiot, I just went along with scheduling it and didn't ask any questions. So I'm asking you guys if you know something I don't. What would the reason for doing an ultrasound at this point be? I'm being induced in a week anyway since my doctor won't let me go over 41 weeks. If the doctor checks on the baby via ultrasound and finds that the baby is small...what will that tell us?? Will it really change anything? I don't want to pay 200+ dollars for an ultrasound that I didn't necessarily NEED, you know? But if it really is beneficial to my health or the baby's, I'm all for it. Help!