Assessment of the dominant abnormal form is useful for predicting the outcome of intracytoplasmic sperm injection in the case of severe teratozoospermia

Purpose: Our purpose was to investigate the relation between the dominant sperm anomaly and sperm morphology and the outcome of intracytoplasmic sperm injection (ICSI). Methods: Two hundred ninety-five patients who underwent a total of 181 cycles of in vitro fertilization (n = 168) and/or 217 cycles of ICSI (n = 177) between July 1995 and May 1997 at Keio University Hospital were investigated. Results: The rates of fertilization and pregnancy were 63.3 and 27.8%, respectively, in ICSI cycles with ≤4% normal forms. When the percentage of strictly normal morphology was ≤4, the fertilization rate was lower in the case of severely tapered head (13.0%; n = 4) than in the cases of other deformities in ICSI. The acrosomal defect made no difference in the fertilization rate with ICSI. Conclusions: The predominant abnormal form affects the ICSI outcome in the case of ≤4% normal forms.