The relationship between follicular fluid aspirate volume and oocyte maturity in in-vitro fertilization cycles

As a consequence of multiple follicular growth during ovarian stimulationfor in-vitro fertilization (IVF), follicles of varying sizes often yieldoocytes that vary in maturity and morphology of the oocyte-cumulus-coronacomplex. The objective of this prospective study was to explore therelationship between follicular fluid aspirate volume and the oocyte'sdevelopmental potential in an IVF treatment cycle. In total 9933 follicleswere studied from 400 patients who underwent 535 consecutive IVF treatmentcycles at St James's University Hospital, Leeds, UK, between February 1995and February 1996. The volume of each individual follicle aspirated wasrecorded and related to the probability of obtaining an oocyte, itsfertilizing capacity, the cleavage rate and the quality of embryos derived.We found no statistically significant difference in oocyte recovery ratesbetween follicles with an aspirate volume < or = 1 ml and follicles witha volume > 1 ml. Although oocytes obtained from follicles with anaspirate volume > or = 1 ml showed a significantly lower fertilizationrate, they went on to cleave at the same rate as oocytes obtained fromlarger follicles and resulted in embryos of comparable quality.Furthermore, there was no statistically significant difference in theimplantation, clinical pregnancy or live birth rates per cycle betweenembryos derived from follicles with an aspirate volume < or = 1 ml andthose derived from follicles with an aspirate volume > 1 ml. We concludethat follicular size and the oocyte's developmental potential in thestimulated ovary are not closely related and can be independent. This is incontrast to the Graafian follicle and the pre-ovulatory oocyte in thenatural cycle.