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.