The Admissions office requested my younger son's grades in January, and made the request directly to his school for their release. I got that word from the Regional Director becasue she knew what his first semester final grades were, and we had not asked the high school to send them. She told me that the Admissions Office had asked for them.
They will ask you for your final transcript as Kamikazi says, but they may do some asking for grades on their own, if the board has questions about how you're doing. My sense tells me that that would likely be in the case of a "bubble" candidate, i.e. someone who's not a definite yes or no.