Combined effects of maternal age and delayed fertilization on the frequency of chromosome anomalies in mice.

Animal experiments indicate that both maternal age and delayed fertilization increase the incidence of chromosome errors in the offspring. In the present study, therefore, we examined how both factors act in combination. We set up normal (0 h delay) and delayed fertilization (6 h delay) subgroups in three different age groups (young, 3-4 months; middle-aged, 9-11 months; and old, 13-15 months), and compared the incidence of chromosome anomalies and other reproductive effects among them. Although the present study confirmed two previous findings that aneuploidies increase with advancing maternal age, and that polyploidies increase with delayed fertilization in mice, it was not clear whether maternal age and delayed fertilization affected the occurrence of aneuploidies either additively or multiplicatively.