Purpose: The present study evaluated the proportions of X-bearing and Y-bearing sperm within the semen of donors who were the declared fathers of three or more sons or daughters.
Methods: The proportions of sperm were determined using dual-color fluorescence in situ hybridization to identify the X and Y chromosomes.
Results: The only difference observed was in semen volume. There was no increase in the proportion of Y-bearing sperm for men with only sons (49.7 +/- 1.3%) or of X-bearing sperm for men with only daughters (44.8 +/- 2.6%).
Conclusions: A preponderance of either sons or daughters in a family cannot be explained simply by an altered ratio of X-bearing and Y-bearing sperm in the father's semen.