Discussion

Two-cell mouse embryos are used twice a week for quality control in the human in vitro fertilization programme at Tygerberg Hospital. If cleavage to the blastocyst stage fails to reach the 90 % level after 72 hours this can be an indication of suboptimal culture conditions. Poor cleavage as the result of a time inter:val between removal of the fallopian tubes and recovery of the embryos was discovered as the result of good documentation of the mouse experimental work. A controlled study was planned to evaluate this observation because poor cleavage led to confusion in the laboratory. These poor results also cause unnecessary preparation of fresh medium and evaluation of the culture conditions in a search for a defect in the system. An explanation for the poor cleavage in the test group could be the development of a low oxygen concentration in the fallopian tube after surgical removal. Mouse embryos fail to develop in the absence of oxygen or when less than 0,56 % is present. 7 It is of the utmost importance to follow a strict protocol in human in vitro fertilization programmes. This simple problem of the time interval also shows that the same strict protocol must be followed with the mouse oocyte quality-control system. Embryos must be obtained immediately after the fallopian tubes have been removed otherwise there will be poor cleavage, and a wild goose chase in the laboratory. The authors wish to thank Sister H. Rosich for her help as research assistant, Mrs L. Brand and Mrs H. Kriiger for the preparation of this manuscript, and Mr P. Africa for his help in the mouse laboratory