The natural elimination of sporadically malformed mouse embryos

Female A/JKt mice greater than or equal to 250 days old had litters with significantly larger fetal resorption rates and offspring with significantly smaller frequencies of sporadic malformations [cleft lip +/- palate (CLP) and open eyelid (OL)] than females < 250 days old. The OL frequency was reduced in litters with resorption as well as in those without, and thus was apparently associated with advanced maternal age per se; whereas the CLP frequency was reduced only in litters with resorption. It seems therefore that the frequency of CLP was reduced in the offspring of older females by preferential elimination and that of OL by another means, perhaps failure to express a tendency.