Is it typical to get an ultrasound at 37 weeks?

At my 36 week appointment, my OB gave me a bit of a red flag. She's pushing a 37 week ultrasound to check the size, 'which is important because it gives a better idea of our delivery options.' Which makes me think she's already throwing out the plausibility of a c-section. My last US was at 32 weeks and measurements were on track. The perinatal doc said if he had to guess, the baby would be about 7-8lbs by delivery. But that was just a guess obviously. My OB hasn't brought up my birth plan at all. And of course my #1 priority is mine and babies safety, but my request is that I try all natural first. I'm scared she's going to push me into a c-section. I'm wondering if I need to hire a last minute doula to advocate for me, or if these late ultrasounds are typical and I'm being paranoid.