P-669 The effect of ovarian follicle size on oocyte fate and embryology outcome

Abstract Study question Does ovarian follicle size influence ultimate oocyte fate and embryology outcome? Summary answer Per punctured follicle, higher yield, MII oocytes, 2PN fertilisation, utilisable blastocyst is observed as increases in up to threshold of 15.5mm What known already It well that maturity probability successful fertilisation correlated the follicles where originated from. However true cutoff ideal at retrieval remains elusive. Furthermore, there no conclusive evidence embryological outcome terms morphology utilisation differs mid large follicular sizes. design, size, duration Prospective observational study undertaken a tertiary fertility referral centre over 10 months. 50 participants recruited underwent conventional controlled stimulation per unit protocol. A total 288 punctures performed period. Participants/materials, setting, methods (OR) procedures were performed. The was individually measured using transvaginal ultrasound. 3 oocytes patient collected for be cultured allow tracking embryo outcomes. Follicular fluid spent culture media separately subsequent metabolomics analysis. sizes divided into 6 groups ( < =9.5, 10-12.5, 13-15.5, 16-19.5, 20-23.5, > =24). Main results role chance Oocyte included 113 mature 83 bipronuclear (2PN) 7 cleavage stage embryos, 39 good quality blastocysts suitable fresh or frozen transfer cycles. When compared overall average an association proportion increases. change appears when beyond optimal may reach plateau. Proportion good-quality associated with rates follow- 0% (less than 10mm), 11.1% (10-12.5mm), 13.2% (13-15.5mm), 15.9% (16-19.5mm), 14.5% (20-23.5mm), 20% (above 24mm). 23 embryos have been utilised date, yielding 50% positive pregnancy rate. Of these resulting test, 81.8% from above 15.5mm. Metabolomics analysis ongoing. Limitations, reasons caution nature along small sample are limitations did not clinical significance observed. Wider implications findings retrieved less 10mm futile. There plateau real detriment demonstrated. This important guide stimulation, especially cases asynchronous growth sacrifice larger commonly assumed. Trial registration number Not applicable