Optimising Follicular Growth for Oocyte Retrieval during IVF Treatment


Lisa Jeffers, Ali Abbara, Waljit Dhillo, Sophie Clarke, Imperial College Healthcare NHS Trust


Background: In vitro fertilisation (IVF) is a valuable treatment for infertility, however insufficient egg (oocyte) retrieval frequently results in cycle cancellation. A trigger injection is administered once three ovarian follicles are ≥18mm in diameter, to provide luteinising hormone (LH)-like exposure to mature oocytes in readiness for retrieval. However, this leading follicle size threshold is not evidence-based and the optimal follicular size for triggering oocyte maturation is not currently known. This study aims to identify the category of follicle diameters that should yield an oocyte if effective triggering is administered.


Methods: A retrospective analysis of datasets generated from three clinical trials using three triggers of oocyte maturation was conducted. Data from 358 patients was analysed: gonadotrophin releasing hormone agonist (GnRHa; n=165), human chorionic gonadotrophin (hCG; n=20) and kisspeptin-54 (KP; n=173). GnRHa and hCG data were collected at My Duc Hospital, Vietnam and KP data at Hammersmith Hospital IVF unit, London. Patients with the highest hormonal response to triggering were selected to ensure effective triggering had been administered. Linear regression analysis was used to identify the category of follicle size that best predicted the number of oocytes retrieved.


Results: The optimal category of follicle size was: 10-17mm for GnRHa (r2=0.46, P<0.001), 13-17mm for KP (r2=0.73, P=0.004) and 13-18mm for hCG (r2=0.42, P=0.022). ‘Oocyte yield’ is defined as the proportion of mature oocytes collected from follicle sizes sufficient to yield an oocyte, and represents a measure of trigger efficacy. KP achieved 100% oocyte yield at effective doses of 12.8nmol/kg or more to generate a serum LH level of ≥10iU/L at 12hrs following administration. hCG and GnRHa achieved optimal oocyte yields at the doses tested.


Conclusion: Identifying the target category of follicular size will guide IVF clinicians in appropriate timing of the trigger injection and accurate evaluation of trigger efficacy.