Minor neurological dysfunction from birth to 12 years. I: Increase during late school-age.

To study the hypothesis that the frequency of minor neurological dysfunction (MND) stabilizes around the age of nine years, two groups of the Groningen Perinatal Project (GPP) were re-examined at 12 years. The study group (N = 174) was selected on the basis of the presence of MND at nine years; the control group comprised 172 neurologically normal children. The hypothesis was rejected: extrapolation of the findings to the total GPP population showed that the over-all rate of MND increased. Control children who developed MND were mainly boys who had been neurologically abnormal at birth or were born preterm and/or had experienced an adversity in combination with asphyxia. Interval complications between nine and 12 years were related to the emergence of MND.