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About 5% of all children go through a period of stuttering that lasts six months or more. Three-quarters of those who begin to stutter will recover by late childhood, leaving about 1% of the population with a long-term problem. The sex ratio for stuttering appears to be equal at the onset of the disorder, but studies indicate that among those children who continue to stutter, that is, school-age children, there are three to four times as many boys who stutter as there are girls.4 Risk factors that predict a chronic problem rather than spontaneous recovery include:*

Family history
There is now strong evidence that almost half of all children who stutter have a family member who stutters. The risk that the child is actually stuttering instead of just having normal disfluencies increases if that family member is still stuttering. There is less risk if the family member outgrew stuttering as a child.

Age at onset
Children who begin stuttering before age 3 1/2 are more likely to outgrow stuttering; if the child begins stuttering before age 3, there is a much better chance she will outgrow it within 6 months.

Time since onset
Between 75% and 80% of all children who begin stuttering will stop within 12 to 24 months without speech therapy. If the child has been stuttering longer than 6 months, he may be less likely to outgrow it on his own. If he has been stuttering longer than 12 months, there is an even smaller likelihood he will outgrow it on his own.

Girls are more likely than boys to outgrow stuttering. In fact, three to four boys continue to stutter for every girl who stutters. Why this difference? First, it appears that during early childhood, there are innate differences between boys' and girls' speech and language abilities. Second, during this same period, parents, family members, and others often react to boys somewhat differently than girls. Therefore, it may be that more boys stutter than girls because of basic differences in boys' speech and language abilities and differences in their interactions with others.

Other speech and language factors
A child who speaks clearly with few, if any, speech errors would be more likely to outgrow stuttering than a child whose speech errors make him difficult to understand. If the child makes frequent speech errors such as substituting one sound for another or leaving sounds out of words, or has trouble following directions, there should be more concern. The most recent findings dispel previous reports that children who begin stuttering have, as a group, lower language skills. On the contrary, there are indications that they are well within the norms or above. Advanced language skills appear to be even more of a risk factor for children whose stuttering persists.

At present, none of these risk factors appears, by itself, sufficient
to indicate a chronic problem; rather it is the cumulative or additive nature of
such factors that appears to differentiate children for whom stuttering comes and goes versus those for whom stuttering comes and stays.

*Longitudinal research studies by Drs. Ehud Yairi and Nicoline G. Ambrose and colleagues at the University of Illinois provide excellent new information about the development of stuttering in
early childhood. Their findings are helping speech-language pathologists determine who is most likely to outgrow stuttering versus who is most likely to develop a lifelong stuttering problem.
Research reports include:
Yairi, E. & Ambrose, N. (1992). A longitudinal study of stuttering in children: A preliminary report. Journal of Speech, Language, and Hearing Research, 35, 755-760.
Ambrose, N. & Yairi, E. (1999). Normative disfluency data for early childhood stuttering. Journal of Speech, Language, and Hearing Research, 42, 895-909.
Yairi, E. & Ambrose, N. (1999). Early childhood stuttering I: Persistence and recovery rates. Journal of Speech, Language, and Hearing Research, 42, 1097-1112.
Yairi, E. & Ambrose, N. (2005). Early Childhood Stuttering: For Clinicians by Clinicians, ProEd, Austin, TX.

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    14. Yairi, E. & Ambrose, N. (2005). Early Childhood Stuttering: For Clinicians By Clinicians, ProEd, Austin, TX.

Guitar, B., & Conture, E. G. (Eds.) (2006). The child who stutters: To the pediatrician. Third edition, publication 0023. Memphis, TN: Stuttering Foundation of America.