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Immediate Insemination of Human Oocytes by IVF or ICSI does not Reduce Fertilization Rates.

This Research Presented at the Pacific Coast Fertility Society, La Costa, California, 1999.

CA Adams, LS Anderson, B Hansen and SH wood. Reproductive Sciences Center, 4150 Regents Park Row, Suite 280, La Jolla, CA 92037

Objective: Early IVF studies suggest that fertilization rates are enhanced when metaphase II oocytes are cultured for 4-6 hours prior to insemination to allow complete nuclear and cytoplasmic maturation. The aim of this study was to compare IVF and ICSI fertilization rates with and without a 4-6 hour preincubation period. Design: 326 consecutive ART procedures performed during a 2-year period were assessed retrospectively. All IVF and ICSI procedures were performed in a consistent manner by the same laboratory staff members. Data was analyzed using the unpaired t-test. Results: 137 IVF procedures were reviewed: Group (a) 70 cases in which oocytes were cultured at least 4 hours prior to insemination and group (b) 67 cases in which sperm was added within two hours of oocyte recovery. Mean age of patients in both groups was 34 years. A total of 555 oocytes were inseminated in (a) resulting in a total fertilization rate of 81% (75% 2PN, 6% 3PN). In (b) with 317 oocytes, total fertilization rate was 80%, (78% 2PN, 3% 3PN). 189 ICSI procedures were examined: Oocytes were either injected after at least 4 hours incubation (105 cases; group c) or within 3 hours of retrieval ( 84 cases; group d). Mean patient age (34 years) was the same in (c) and (d). 1254 oocytes was inseminated in group (c) resulting in a total fertilization rate of 68%, (67% 2PN, 2% 3PN). In group (d) 800 oocytes were inseminated resulting in 69% fertilization (67% 2PN, 2% 3PN). Clinical pregnancy rates per embryo transfer in the four groups were: (a) 34%, (b) 51%, (c) 42%, and (d) 43% indicating no decrease in IVF or ICSI pregnancy rates when insemination was performed immediately after oocyte retrieval. Conclusions: Preincubation of oocytes prior to IVF or ICSI insemination did not affect fertilization rates, therefore, insemination of metaphase II oocytes by IVF or ICSI may be performed immediately after oocyte retrieval. In terms of IVF pregnancy rates, it may even be beneficial to inseminate oocytes soon after retrieval. Such flexibility allows embryologists to maximize work efficiency in addition to providing optimal ART results.