IVF baseline and bloodwork-are you on your period for it?

I’m on an antagonist protocol and was told to take my last birth control Thursday and go in Friday morning at 7am for my baseline ultrasound and bloodwork. But my body wouldn’t have recognized I’m off birth control yet so I’m confused why they’d have my baseline when I wouldn’t be bleeding full flow? I’m always used to having a baseline scan on cycle day 2-3, I left a message for the nurse but just looking for others experience! I’ll be starting injections Sunday evening which would be cycle day 3 stopping BC Thursday.