Is one round of b/w and sono prior to transfer enough??

Hi all

Question: I am on my first DE cycle. Retrieval is (tentatively) scheduled for this Saturday, with transfer 3-5 days later. For this whole cycle, I have only had one monitoring session (b/w & sono), which was last Monday (April 14). This does not seem like enough to me, to make sure I am where I should be prior to transfer. However, the RE's office does not seem to think I need to come in again.
but is just one round of b/w and sono prior to transfer really enough??

thanks!