Infantile spasms???

How do I know the difference between infantile spasms or just baby development?? I feel so stupid. I took my 3 month old to the doc yesterday bc she has a cold. But somehow forgot to mention these little spasms that she keeps having. It’s her arms and hands they wave, like shake in the air. A lot. I have no idea if it’s normal development or not. And I feel really dumb I didn’t ask at the doctor yesterday.