Nervous about finding out gender today?

I made 23 weeks today and finally go in for my anatomy scan in a little bit. We will (hopefully) find out gender. My boyfriend is so stuck on having a boy and has expressed many times how disappointed he'll be if it's a girl. I have a 5 year old daughter from a previous relationship and she is dying for a sister. Someone will be disappointed and that is part of what makes me nervous. The other part is worrying about the baby's health and if there may be some sort of defect.