High risk doctor

I go to see the high risk ob tomorrow due to having a single artery umbilical cord (most umbilical cords have 3 vessels, mine has 2). I'm pretty nervous even though I have read in many different places that 85-90% of the time the 2 vessels make up for the lack of the third. My fingers are crossed for a good appointment! Thank goodness the appointment is in the afternoon, I'm working 11p-7a tonight...can't wait to get some sleep!