My puppymill rescue has dew claws on her back legs. When the rescue spayed her, they weren't removed, so I didn't think it was worth having her put under anesthesia just for removal. I just have to be careful not to catch them when combing her out and keep them trimmed. If I'm not doing nails myself, I have to specifically mention she has them on her back legs since they are often missed under all her hair.
I would have it removed when you have your puppy spayed/neutered.
