The effect of embryo transfer on the intrauterine growth of the mandible in mouse fetuses.

A DDD/Qdj strain of embryos was transferred to the same strain of recipient females to examine the effect of the embryo transfer procedure on the intrauterine growth of the mandible in mouse fetuses. Just after parturition, the litter size and the gestation period were recorded and the mandibular size of the newborn offspring was measured by use of an image analyzing system. The mandibular size of the newborn offspring developed from the transferred embryos was compared with that of the newborn offspring developed from the nontransferred embryos. The following results were obtained: 1) There was no gender difference in the mandibular size of the newborn offspring from either the transferred or nontransferred embryos. 2) An inverse relation between the litter size and the mandibular size of the newborn offspring was observed, while a direct relation between the gestation period and the mandibular size of the newborn offspring was observed. 3) The litter size in the transferred group was smaller than that of the nontransferred group, while the gestation period in the transferred group was longer than that of the non-transferred group. After adjusting for the effects of the litter size and the gestation period on the mandibular size for both groups, the adjusted mandibular size of the newborn offspring in the transferred group was significantly smaller than that of the nontransferred group. Thus, it is concluded that the embryo transfer procedure retards the intrauterine growth of the mandible in mouse fetuses developed from transferred embryos.