Abstract: "The pregnancy of the recipients and survival rate of founder mice during the production of transgenic mice with twelve genes were studied. The results showed that 75 of 98 pregnant recipiens had parturition 19～21 days after embryo transference and the survival rate of their progenies was 93.5% (374/400). 16 of 98 pregnancy recipients had natural parturition 22～24 days after embryo transference, 7 of 98 pregnancy recipients had parturition by cesarean section 22～23 days after embryo transference, and the survival rates of their progenies were 0% (0/52) and 60.7% (17/28) respectively. The results indicated that the pregnancy of recipients was similar to that of normal ICR mouse. The survival rate of the progenies from cesarean section is higher than that of those from natural parturition in prolonged pregnancy recipients. "