Dilation at Baseline?

JEN • Married 12/31/11 TTC since 1/1/12. We suffered a mc 12/23/14 :( started 2015 we did injections, still BFN, did 1 IUI BFN finally moved to IVF (long lupron protcol) in Sept. BFP! EDD 07/17/16
I was told that based on my trial transfer I would need dilation at my baseline appt (next week) can anyone tell me what to expect?