How long should a perinatology appointment last?

At my regular appointment for my pregnancy, my OBGYN noticed that the umbilical cord was a 2 vessel cord instead of a 3 and scheduled to have me go to a Perinatal specialist tomorrow to get things checked further for safety reasons. I am just curious to see about how long an appointment like this lasts and what I can expect from it. I'm rather nervous about everything, even though my doctor said not to worry and some advice and information would be helpful! Thanks