I'm not sure what a baseline appointment is, but I know I had tests done on CD3 and that was to check Estrogen/FSH and whatever else.
Sorry, maybe someone else knows.
I usually go for my baseline appt btwn day 1 and 3 of cycle. The RE does a transvaginal ultrasound to look at your ovaries and check to see if there are any exsisting follies (cysts) sometimes there are little cysts left. I think they want to make sure that they are not watching those ones. Your next u/s they will check the size and amount of follies and your lining of your uterus. (I am on follistim and usually have 3 or 4 good eggs every month) Make sure that you tell them is you feel extremely bloated or pain. Follistim is strong and has a potential to cause over stimulation. Good luck