In vitro fertilization failure: Identification of gamete defects by investigation of sperm-zona pellucida binding capacity of unfertilized oocytes
The objective of the study was to determine whether fertilization failure was due to spermatozoal or oocyte factors. Twenty-five unfertilized oocytes and from 12 IVF/GIFT couples showing total or partial fertilization failure were evaluated for sperm zona binding potential under hemizona assay (HZA) conditions. Hemizonae were separately incubated with a sperm sample from the husband and that of a fertile control. Tight sperm binding to hemizonae was assessed. First, among the 12 patients, result showed a possible zona defect thought to be the cause of fertilization failure in five cases. Second, in two cases, fertilization failure was possibly caused by poor sperm binding potential of spermatozoa. Third in two cases, fertilization failure was possibly caused by an oocyte defect, and fourth, three cases showed a mixture of possible causes. The results stress the need to develop a sequential analytic programme for those couples with repeated total or partial fertilization failure.