Stammering, also known as stuttering, usually begins between the ages of 2 and 5 years of age. Typically, children will go through a short phase of dysfluency (disruptions in the flow or fluency of speech) as they rapidly learn new words and start to make sentences. During this time, they may repeat whole words, hesitate and rephrase as they are working out what they want to say. However, these repetitions tend to sound easy, occur occasionally and disappear over a few months.
For a small percentage of children, these dysfluencies can start to sound more effortful, more frequent, and may cause upset to the child. Young children may even start to avoid talking to friends, answering questions at school and become less confident.
If you are worried about your child's speech development, and particularly if s/he is showing awareness and/or becoming upset about their speech, it is best to talk to a GP or Speech & Language Therapist. It is better to seek support rather than wait and see.