The effect of extended culture of cumulus-oocyte complexes in follicular fluid during in vitro fertilisation cycles.

Purpose: To assess the clinical and biological effect of the preincubation of oocytes in follicular fluid prior to IVF and ICSI cycles.

Methods: A series of patients were treated by the preincubation of oocytes in the patients' follicular fluid for 3 h after oocyte retrieval followed by processing with standard protocols. Control oocytes were preincubated in normal IVF culture medium. Fluorescence techniques were used to examine oocyte mitochondrial membrane potential.

Results: Fertilisation, pregnancy, and implantation rates were all significantly improved after the preincubation of oocytes in follicular fluid. Further tests suggested that differences in pH between follicular fluid and artificial culture medium may be critical to these differences.

Conclusions: Preincubation of human oocytes in follicular fluid improves the results after IVF. This may be partly due to the use of a non-"physiological" pH in artificial culture media during in vitro fertilisation procedures.