Disclosed is a medium for the propagation of early stage embryos to blastocyststage. The medium contains an effective amount of human GM-CSF to increase thepercentage of pre-blastocyst embryos which develop to transfer readyblastocysts. Also disclosed is a method of growing early stage human embryosto transfer ready blastocysts. The method includes the step of incubating theembryos in vitro in a culture medium containing an effective amount of humanGM-CSF for a time and under conditions to increase the proportion of transferready blastocysts. An IVF program that includes the method of growing earlystage human embryos to transfer ready blastocysts is also disclosed.
