Pretreatment of sperm with low hypo-osmotic swelling tests with chymotrypsin prior to intrauterine insemination (IUI) and avoidance of unprotectected intercourse results in pregnancy rates comparable to IUI for other male factor problems.

Purpose: To carry out a retrospectively performed matched controlled study to determine the efficacy of pretreatment of sperm having low hypo-osmotic swelling (HOS) test scores with chymotrypsin galactose prior to intrauterine insemination (IUI) compared to IUI for other types of male factor problems. The women with male partners with low HOS scores were advised not to have unprotected intercourse.

Methods: All cycles having IUI with chymotrypsin treated sperm for low HOS scores were matched with the very next woman having IUI for sperm with other male factor problems but with normal HOS scores.

Results: There was a significantly higher clinical pregnancy rate with chymotrypsin treated sperm (32.3% per IUI) vs. 21.9% for other male factor cases. The live birth rate per IUI cycle was not significantly different (21.2% vs. 15.4%).

Conclusions: These results now show that pretreatment of sperm with low HOS scores allows very good pregnancy rates following IUI as long as the couple is cautioned about unprotected intercourse. These data support the concept that sperm with low HOS test scores impair fertility by transferring a toxic factor from the sperm to the zona pellucida to the embryo membrane which impairs the embryos from implanting.