Frequency and patterns of premature sperm chromosome condensation in oocytes failing to fertilize after intracytoplasmic sperm injection

Abstract

Purpose: The purpose of this study was to evaluate reasons for fertilization failure after intracytoplasmic sperm injection as a part of internal quality control and to review corresponding previous data.

Methods: One hundred injected but unfertilized oocytes were fixed and examined after Giemsa staining.

Results: Three oocytes (3.0%) did not show the presence of a spermatozoon and two (2.0%) contained pronuclear structures. An intact spermatozoon was found in 25 cases (25.0%), whereas the sperm nucleus had undergone premature chromosome condensation (PCC) in 70 cells (70.0%). A modified classification system was established to characterize the different PCC patterns.

Conclusions: PCC indicates a correct intracytoplasmic injection and excludes technical problems as a major reason for fertilization failure in the present study. A lack of oocyte activation due to cytoplasmic immaturity is considered responsible for the occurrence of PCC. A review of the literature shows that the role of sperm chromatin abnormalities in the process of nuclear decondensation needs further investigation.