Consequences of Asynchronous Follicle Growth during Controlled Ovarian Stimulation: Management Strategy

GnRH antagonists protocol for controlled ovarian stimulation (COS) in IVF can cause an asynchronous ovarian growth that may interfere with cycle outcome. In this retrospective study, 313 antagonist cycles with a leading follicle ≥ 16 mm detected on first control were compared to 247 controls. If an asynchronous follicle and E2 less than 600 pg/ml were detected, antagonist was delayed. Main objective of this study was to verify if asynchronous cycle management strategy was able to overcome possible adverse cycles outcomes compared to synchronic cycles. Both groups were comparable in terms of age, antral follicle count, starting dose, OC pill use or male factor. In the asynchronous group, a higher number of cystic follicles were seen but no significant differences were found in stimulation length, final follicle number, E2 level, number and mature ovocytes or embryo number and quality. Fecundation rate was higher with lower implantation and cancellation rate. No differences were found in pregnancy rate, miscarriage rate, multiple pregnancy rate or live birth rate. Our strategy allowed us to reach similar stimulation length with lower cancellation rate and no differences on final follicle number and E2. No impairment in ovocyte quality was detected as no differences appeared in ovocytes or embryos parameters fecundation rate was higher. Nevertheless, implantation rate was significantly lower in the asynchronous group pointing at a deleterious effect in endometrial receptivity.