Will I have vaginal birth or C-section

Friday I had my last ultrasound at 38 weeks, my girl is weighing in right now at 8 pounds 3 ounces. I'm worried I'm going to have to have a c-section because they said she's long, her head is 90% percentile & she's big. Im only 17 so idk if that effects it or not. Got ob appointment tomorrow but wanna know ahead what you guys think!