Background: The aim of the present study was to determine whether parental age has any influence on child health., Methods: Well-baby check-up data at 1 month and at 12 months of age were used. The trends of parental age in association with growth measurements, incidence of physical and developmental abnormalities, occurrence of low birthweight, and maternal history of spontaneous abortion were analyzed., Results: Associations between increasing paternal age and incidence of psychomotor developmental delay at 12 months, increasing paternal and maternal age and increasing birthweight, and increasing parental age and higher incidence of history of spontaneous abortion were found. The incidence of low-birthweight infants was significantly decreased with increasing paternal age., Conclusions: Not only increasing maternal age but also increasing paternal age have influences on child development and growth in the general population., (© 2011 The Authors. Pediatrics International © 2011 Japan Pediatric Society.)