Fertilization and pregnancy with acrosome intact sperm by intracytoplasmic sperm injection in patients with disordered zona pellucida-induced acrosome reaction.

OBJECTIVE

To determine whether fertilization and pregnancy could be obtained by injection of acrosome-intact sperm into the cytoplasm in patients with persistent failure of fertilization in IVF-ET associated with disordered zona pellucida (ZP)-induced acrosome reaction (AR).

DESIGN

Sperm-ZP binding and penetration and ZP-induced AR were compared between patients and fertile donors. Acrosome-intact sperm removed from the ZP were injected into the cytoplasm of the oocytes.

SETTING

Reproductive Biology Unit, Royal Women's Hospital.

MAIN OUTCOME MEASURES

The proportion of ZP penetrated and ZP-induced AR and fertilization and pregnancy after intracytoplasmic sperm injection were analyzed.

RESULTS

Most (7/8) of the patients had consistently normal sperm characteristics including concentration, motility and velocity, acrosomes, and morphology. Mean number of sperm bound to the ZP was not significantly different between patients (97 sperm/ZP) and fertile donor controls (100 sperm/ZP). However, AR of sperm bound to the ZP was significantly lower in the patients (4%) than in controls (61%). None of the ZP (n = 32) were penetrated by patient sperm whereas all (n = 32) ZP were penetrated by control sperm. Acrosome intact sperm removed from the ZP were used for intracytoplasmic sperm injection. All patients had > or = 50% normal fertilization and embryo development. Three pregnancies (one early aborted, two ongoing) were achieved after the transfer of fresh or frozen embryos.

CONCLUSION

Acrosome-intact human sperm can produce a high fertilization rate and pregnancies after intracytoplasmic sperm injection in patients with disordered ZP-induced AR. The acrosome reaction is unlikely to be important for fertilization with intracytoplasmic sperm injection.