Although many definitions of reading fluency include only rate, accuracy, and expression, we include comprehension in our definition of reading fluency. We do so, because without understanding, reading becomes only word calling. Therefore, reading fluency involves more than just accuracy and rate. Your child should be able to read fluently and understanding.
Including comprehension in a definition of reading fluency brings comprehension to the forefront, putting a focus on it as the purpose for fluent reading.