I did when I was pregnant because the doctor thought I wasn't gaining enough weight in the first trimester (even though I was... she was probably just used to seeing pregnant butter huffers who gained 20+ pounds by that point). Anyways, he had a few suggestions for ways I could get more protein and calcuim. I went to see him again when it was time to start feeding my baby solids because I wanted to make all his food at home and had no idea what I was doing. Other than special circumstances similar to those, I can't imagine why a human would need to consult a dietician.