Comparison of bicarbonate and HEPES-buffered media on pregnancy rates after intrauterine insemination with cryopreserved donor sperm

OBJECTIVE: We compared the pregnancy rates (PRs) after intrauterine insemination (IUI) with frozen donor sperm prepared in Ham's F-10 medium (Irvine Scientific, Santa Ana, CA) with bicarbonate buffer and synthetic human tubal fluid with HEPES buffer (Irvine Scientific). DESIGN: Women (n = 101) were randomized upon entry into the program, receiving sperm prepared in either Ham's F-10 or human tubal fluid medium their first treatment cycle. If pregnancy did not occur, the alternate medium was used to prepared sperm for the following cycle. SETTING: All patients were treated in our private care center. PATIENTS: Patients entering this study were normally ovulating women undergoing IUI with frozen donor sperm. MAIN OUTCOME MEASURE: Pregnancy was used as our main outcome measure of success. RESULTS: After 324 cycles of treatment, the PR per cycle of IUI was 17.5% with sperm prepared in human tubal fluid which was significantly different (P = 0.05) from the PR (9.8%) after insemination with sperm prepared in Ham's F-10. There was no statistical difference in the number of motile cells inseminated in each of these groups. CONCLUSIONS: Transitory exposure of the sperm in Ham's F-10 medium to the environment during preparation for insemination may result in an alkalinization of the medium that has a lasting influence on sperm fertility.