my three year old also stuttered, but it was MUCH more pronounced when he was tired or upset or frustrated about something. i spoke to a speech therapist about it, and she also recommended ignoring it. she said dont make him repeat himself, just figure out on your own what he wants to say and answer him. its been almost 6 months, and its really gotten much better. now its REALLY only when hes tired or whatever.
also, keep in mind that it is an age typical thing, which is why most therapists will tell you to ignore it.
i would suggest that you keep an eye on it for another 3 months, and if it EITHER doesnt get better OR if it gets worse, speak to a therapist about having your child evaluated.
hatzlacha raba!!