Sub-optimal responders following controlled ovarian stimulation: an overlooked group?

Individualization of IVF treatment and tailored stimulation based on predicted ovarian response may maximize treatment success and minimize the risks following IVF. Whilst there has been a consensus in defining poor ovarian response and an attempt to elucidate the threshold for excessive ovarian response based on the number of oocytes retrieved following ovarian stimulation, no systematic effort has been made in order to refine the oocyte yield thresholds for a normal responder. In this opinion article we discuss the evidence behind the oocyte number thresholds for the ovarian response categories and present the rationale and merits in recognizing a new, overlooked, ovarian response group: The sub-optimal ovarian responders.