What is the earliest week you can see the gender?!

jade7kb

I have read that you can see the gender as early as 13 weeks, which is what I am now.  I have an appointment to go in Wednesday to check for deformaties and things like that and they have to do an ultrasound for it.  I was hoping we would be able to see what it was!  We are excited and my husband wants a boy, we already have a girl and I don;t care either way, but it would be nice to start buying stuff!