THE CORRELATION BETWEEN FOLLICULAR MEASUREMENTS, OOCYTE MORPHOLOGY, AND FERTILIZATION RATES IN AN IN-VITRO FERTILIZATION PROGRAM

Objective: To explore the relationship between follicle size and the m orphology of the oocyte-cumulus-corona complex with fertilization rate s in stimulated cycles of IVF. Design: Retrospective comparison of mea surements and observations of 2,429 oocytes from 215 patients undergoi ng 324 stimulated IVF cycles. Setting: A large hospital-based IVF prog ram. Main Outcome Measures: Individual follicles were measured by ultr asound before transvaginal aspiration and the size was recorded. The o ocyte-cumulus-corona complex from each follicle was examined and class ified. The oocytes were checked for evidence of fertilization 17 to 22 hours after insemination. Results: The fertilization rate of all oocy tes regardless of morphological type revealed a positive linear correl ation with increasing follicle diameter. The fertilization rates of ty pe I oocytes was marginally higher than type II oocytes, controlling f or follicle diameter; however, this difference did not achieve statist ical significance. Oocytes from follicles with a mean diameter greater than or equal to 16 mm had significantly higher fertilization rates t han did oocytes from follicles with a mean diameter less than or equal to 14 mm. Conclusions: Follicle size is a better predictor of fertili zation than is morphological characterization of the oocyte-cumulus-co rona complex in IVF.