Clinical definition paper on in vitro maturation of human oocytes.

In vitro maturation (IVM) of human oocytes is a reproductive technique which has been practiced for 25 years and is gaining popularity. However, the techniques used for IVM differ substantially across clinics and they result in extremely variable pregnancy rates, partially due to some of these differences in protocols. Such differences include the use in some cycles of hCG triggering prior to oocyte retrieval and the use of a few days of gonadotrophin treatment to support moderate follicle growth. Other important factors are patient selection (including those with polycystic ovaries or decreased ovarian reserve), the number of embryos transferred and cleavage-stage embryo or blastocyst transfer. There are also substantial differences of opinion among clinicians regarding IVM and what it implies. Due to the large variation in protocols, a decision was made to write this paper in an attempt to introduce uniformity when comparing treatments and outcomes of IVM. A clinical definition of IVM was developed: The retrieval of oocytes from small and intermediate sized follicles in an ovary before the largest follicle has surpassed 13 mm in mean diameter. The use of short gonadotrophin stimulation should be acknowledged. However, it should be stated that metaphase II oocytes also have the potential to be collected at that time in the cycles associated with either hCG or GnRH agonist priming. Many feel this is not IVM because some mature oocytes are retrieved, therefore, we recommend renaming this procedure either natural cycle IVF or modified natural cycle IVF (if gonadotrophin stimulation is given) with early triggering, combined with IVM The percentage as well as the absolute number of mature oocytes at retrieval should be indicated. The use of these titles will allow transparency when comparing results of IVM cycles.