IVM in need of clear definitions

Abstract

Oocyte in vitro maturation (IVM) involves the achievement of the process of oocyte maturation in vitro. Clinically, it was introduced several decades ago as a potentially more patient-friendly and less expensive assisted reproductive technology (ART) approach, as immature oocytes collected from mid-antral follicles can be matured in vitro without prior gonadotrophin stimulation. However, IVM oocytes are developmentally less competent compared with oocytes matured in vivo, a fact that has encouraged the use of short FSH priming and/orhCGtriggering in IVM cycles. These alternatives have generated much confusion about the definition and clinical outcome of IVM, also among ART specialists, especially because hCG triggering can support maturation in vivo even in follicles of 10-13 mm in diameter. In a recent manuscript, a team of IVM specialists propose that IVM should include any ARTapproach involving the collection of oocyte from small and intermediate sized follicles even afterhCG or GnRH triggering. It is more than predictable that other scientists and clinicians with an interest in IVM will object to such a definition, believing that semantically and operatively IVM should not be associated with pharmacological interventions aimed at promoting or achieving maturation in vivo, although partially.