Paternal age and Down syndrome.

The frequency of Down syndrome (DS) in infants of older fathers has been examined in two sets of data. The effect of maternal age was controlled by single years of age. Lack of tight control has been an important weakness of other studies on this subject. Data obtained in metropolitan Atlanta by an intensive case-ascertainment program showed no overall excess of DS infants born to older fathers. Nor was there evidence of such an effect in recent birth certificate data made available by the National Center for Health Statistics. The Atlanta data suggest an increased number of DS infants born to older fathers who had children by women less than or equal to 34 years. However, there was a small deficiency of DS infants born to older fathers by women greater than or equal to 35 years. The possibility of a paternal-age effect remains open, but the available data suggest that, if it exists, it is quite small.