Paternal age and Down's syndrome diagnosed prenatally: no association in French data.

An investigation of a paternal age effect independent of maternal age was undertaken for 118 trisomy 21 cases diagnosed prenatally in 6656 amniocenteses. The mean of the difference delta in paternal age of Down's syndrome cases compared to those with normal genotypes after controlling for maternal age was +0.46 with a 95 per cent confidence interval of -0.84 to +1.76. This revealed no evidence for a paternal age effect. Multiple applications of the Mantel-Haenszel test revealed no statistically significant evidence for a paternal age effect independent of maternal age. These results are in agreement with those of Hook and Cross (1982b) but not with claims of Stene et al. (1981), of a strong paternal age effect detected in studies on prenatal diagnosis. The hypothesis suggested by Hook and Cross (1982a) that there is a rather weak paternal age effect independent of maternal age in most if not all populations cannot be excluded. If temporal or geographic factors account for the differences in studies on paternal age effect, extrapolation to other time periods or populations cannot be done.