Culture factors in relation to the success of human in vitro fertilization and embryo transfer

The development of 1-cell mouse zygotes to the blastocyst stage in vitro has been used as a quality control for the media employed for human in vitro fertilization and embryo transfer (IVF-ET). The following procedures were associated with high rates of mouse embryo development and human pregnancies following IVF-ET: adequate gassing and equilibration of the medium, double rinsing of pipettes and catheters used to handle embryos, use of a HEPES-buffered medium for manipulating embryos in the absence of an atmosphere containing 5% CO2, control of excessive temperature in the vicinity of the embryos, and ET using medium containing 50% patient's serum. The institution of these procedures gave more consistent pregnancy rates. However, there was no obvious association between fertilization and cleavage of human oocytes and the quality of the medium ascertained by the mouse embryo development test.