In vitro fertilization with intracytoplasmic sperm injection is an effective therapy for male factor infertility related to subnormal hypo-osmotic swelling test scores

The aim of the study was to determine if intracytoplasmic sperm injection ( ICSI) would be an effective therapy for males with subnormal hypo-osmotic s welling test (HOST) scores, a condition known to prevent implantation of em bryos despite allowing normal fertilization and embryo formation. Couples i n whom the male partner had a HOST score of <50% and failed to achieve a pr egnancy despite at least 3 cycles of intrauterine insemination with chymotr ypsin-galactose-treated sperm were treated with in vitro fertilization (IVF ) with ICSI. The clinical and viable pregnancy rates were 49.0% and 45.3% ( n = 53). The implantation rate was 27.1%. These data thus demonstrate that ICSI is an effective therapy for infertile couples in whom the male partner has a subnormal hypo-osmotic swelling (HOS) score. Previous studies using conventional IVF without ICSI when HOS was subnormal found normal fertiliza tion rates but a marked reduction in pregnancy and implantation rates. The very acceptable pregnancy and implantation rates demonstrated in this study with ICSI is consistent with the hypothesis that the defect associated wit h sperm that have subnormal HOST scores is not related to the single sperma tozoon that is responsible for fertilizing the oocyte but may be related to a toxic factor associated with the supernumerary sperm attached to the zon a pellucida.