A BRIDGE TO INTRACYTOPLASMIC SPERM INJECTION - HIGH INSEMINATION CONCENTRATIONS BENEFIT PATIENTS WHO HAVE A REDUCED CHANCE OF FERTILIZATIONWITH STANDARD IN-VITRO FERTILIZATION

This study was carried out to determine whether high insemination conc entrations (HIC) could improve fertilization and pregnancy rates in pa tients who had either previously demonstrated poor fertilization rates in vitro using standard protocols (Group 1) or in whom a reduced chan ce of fertilization was indicated at semen assessment prior to in-vitr o fertilization (IVF) (Groups 2 and 3), Forty nine patients were recru ited for the study, Standard IVF was carried out in 1 ml volumes using 10(5) spermatozoa/ ml, HIC treatment involved co-culture of spermatoz oa and oocytes in microdroplets with insemination concentrations incre ased 10-50 fold higher than standard IVF. Fertilization and pregnancy rates were compared between standard IVF and HIC in individual patient s either in consecutive cycles (Group 1) or using sibling oocytes in t he same cycle (Group 2), Group 3 patients were treated with HIC for th eir first treatment cycle, HIC significantly improved the fertilizatio n rate compared with standard IVF for Groups 1 (59.7 +/- 10.7 versus 1 9.6 +/- 5.4% respectively) and 2 (54.9 +/- 8.5 versus 34.0 +/- 8.5% re spectively). HIC increased the pregnancy rate from 0% with standard IV F to 20% per embryo transfer in Group 1 patients. A single pregnancy d erived from the transfer of HIC and IVF embryos occurred in Group 2. T he fertilization rate (47.2 +/- 7.6%) and pregnancy rate (31.3% per em bryo transfer) for Group 3 patients was higher than predicted. There w as no increase in the rate of polyploidy with HIC. Provided there are sufficient numbers of motile spermatozoa, HIC may be offered as an ini tial form of treatment, thus permitting referral of only the poorest r esponders for intracytoplasmic sperm injection (ICSI).