Sometimes they can wiggle enough to get their fingers out when they are a bit older but in general, if you have the right size swaddle for the baby then they won't get their hands out & their arms are secure either at their sides or on their chest (where-ever you put them).

My daughter was a compete swaddle addict so we couldn't just go cold turkey and take her arms out of the woombie. We ended up using another product called the Zipadeezip to transition which worked a treat.