Hi MN2013,
I went to the Fetal Assessment Centre at Pretoria East Hospital. The doctor there was great and she explained everything patiently. I went because of my age (I'm 36) and other factors. We just wanted to be prepared. As a bonus we found out the gender of our baby at the assessment! (at 13 weeks).
I don't think it matters who you go to, it is just important to know why you're going. Good luck with your assessment! Remember that stress is just bad for you and your little one and you can't change anything by stressing about it.