Nervous

Had my last Doctor appt today at 37+5 and babies wt was 5 lbs7oz. Kinda worries me. He said that she not gonna be very big maybe 6 lbs but it's hard to get a good head measurement when baby is so low in the birth canal. Scheduled csection for Friday the 29th. Baby has always measured more than what this app says now suddenly she's under the apps suggested wt. anyone had this happen and actual wt was different at birth.