The high responder: a review of pathophysiology and outcomes during IVF treatment

This review attempts to summarize the known literature on high responders to ovarian stimulation during assisted reproductive techniques (ART). Response to gonadotrophins is subject to significant interindividual and intercycle variation, thus carrying a risk of high response or poor response to ovarian stimulation regimens. The main risk for high responders is the development of ovarian hyperstimulation syndrome (OHSS) which is associated with significant morbidity. Hence, the definition of high responders in the literature has primarily focussed on risk factors for OHSS. Strategies to reduce OHSS including tailoring of the ovarian stimulation regimens and adjusting gonadotrophin doses according to patient characteristics and findings during the cycle of stimulation. In addition, modifying the type of ovulation trigger used and adjuvant therapies, such as metformin, intravenous colloids and vascular endothelial growth factor blockers, have also been studied as options to reduce OHSS. Apart from the risk of OHSS, high response also appears to have an adverse impact on the oocyte and endometrium, though there is a paucity of data regarding the extent and mechanisms behind this impact.