A new more detailed stratification of low responders to ovarian stimulation: from a poor ovarian response to a low prognosis concept

The management of patients with impaired or poor ovarian response (POR) remains a controversial and complex clinical issue. A systematic review of 47 randomized controlled trials revealed 41 different definitions of POR (1). Notably, the number of oocytes retrieved was adopted as a criterion of POR in 40% of the trials, although the threshold number differed considerably among studies (1). To standardize the definition of POR, Ferraretti et al. (2) proposed new criteria, known as the “Bologna criteria,” based on three conditions: 1) advanced maternal age (≥40 years) or any other POR risk factor; 2) a previous incident of POR; and 3) a low ovarian reserve test in terms of antimüllerian hormone (AMH) and antral follicle count (AFC).