sophie-
After interviews a good amount of people are waitlisted...and, a good amount of those people, depending on the school of course, may end up coming off the waitlist.
Take cornell, for instance, where I will be a first year this august (I deferred matriculation for a year) Within my entering class, 40 percent will have come in off the wait list!
So fret not, but instead focus on what you will do should things not work out- better to be safe than sorry- and consider writing a letter to the admissions office explaining why you would love to attend their school, if taken off the waitlist. Also, if you can, try to see if you know anyone at the school, or any doctors who have been your mentors, who might be able to call and find out exactly how high up you are on the list- it will give you a more exact idea of how much of you application you might need to alter should you not get in this year.
All the best!
Elisabeth in NY