Subsequent development during incubation of fertilized mouse ova stressed by high ambient temperatures

Mouse embryos subjected to high temperature stress (heat‐stress) in vivo during the time of first cleavage division, were recovered from the oviducts 48 to 54 hours post‐observance of a copulatory plug. The effects of heat‐stress on development of those embryos incubated in vitro through the blastocyst stage were studied and compared to embryos from mice in a control environment. Heat‐stressed embryos which developed in vivo to ten days gestation were also studied. Development of heat‐stressed embryos was retarded by the time of recovery. There was a significant (P<0.05) decrease in the number of heat‐stressed embryos which became blastocysts in vitro, as compared to control embryos. Also, there were fewer blastocysts from heat‐stressed embryos which hatched during three days of incubation in vitro when compared to controls (56% vs 67% for heat‐stressed and controls, respectively). There was significant (P<0.01) pre‐ and post‐implantation loss of embryos in heat‐stressed females at ten days gestation.