Objective: To analyze the morphological characteristics of oocyte, sperm and blastomere-stage embryo and correlate with intracytoplasmic sperm injection (ICSI) embryo score.
Methods: ICSIs were done in M II oocytes harvested after superovulation with long-protocol gonadotropin releasing homone agonist. Various morphological characteristics of oocyte, sperm and blastomere-stage embryo were identified and correlated with the embryo score.
Results: Forty-three ICSI cycles were completed. Twelve out of 31 male factor infertile couples and 2 out of 12 with fertilization failure during previous standard in vitro fertilization-embryo transfer cycles achieved clinical pregnancy, resulting in a pregnancy rate of 38.7% and 16.7% per transfer respectively. Severe teratospermia and abnormal cytoplasm of the oocytes, such as cytoplasmic central dark granulas, inclusions, had significantly low embryo score (P < 0.01). The size of perivitelline space had no influence on the result. The oocytes without oolemma elasticity during ICSI process had a lower oocyte survival rate compared with those with oolemma elasticity (P < 0.01). The clinical pregnancy rate per transfer between transferred embryo with average score higher and lower than 3 was significantly different (52% vs 10%, P < 0.001).
Conclusion: Some morphological characteristics of gamates correlate with the embryo quality and clinical pregnancy rate. They can be used to assess and improve the clinical management during ICSI.