Predicting the fertilizing potential of human sperm suspensions in vitro: importance of sperm morphology and leukocyte contamination

Abstract

Objective: To determine the relationships between sperm function tests and fertilization of human oocytes in vitro.

Design: Analysis of infertile patients undergoing IVF therapy.

Setting: Diagnostic Andrology Laboratory and Assisted Conception Service.

Patients: Forty-one couples who underwent IVF-ET therapy were studied.

Interventions: None.

Main outcome measures: The ability of human spermatozoa to achieve fertilization in vitro was examined in relation to numerous criteria of semen quality, including the conventional semen profile, the computer-aided assessment of sperm movement, ionophore-induced acrosome reaction, acridine orange staining, sperm morphology, and chemiluminescent signals induced by phorbol ester and N-formyl-methionyl-leucyl-phenylalanine (FMLP).

Results: Significant correlations were observed between fertilization rates and several attributes of the sperm preparations, including elements of sperm function (acrosome reaction), movement (percentage motile, hyperactivation, the amplitude of lateral sperm head displacement), morphology (normal morphology, midpiece defects, multiple anomalies index), nuclear normality (acridine orange staining), and reactive oxygen species generation (chemiluminescence induced by phorbol ester and FMLP). In a stepwise multiple regression analysis, an accurate prediction of fertilization rates was obtained using a multiple regression equation incorporating six variables of which sperm morphology and FMLP-induced chemiluminescence were the most informative.

Conclusions: A set of criteria have been identified that accurately predict the fertilizing potential of human sperm suspensions in vitro and that place particular emphasis on sperm morphology and the degree of leukocyte contamination.