Selective microsurgical removal of a pronucleus from tripronuclear human oocytes to restore diploidy: disregarded but valuable?

ObjectiveTo review data on the microsurgical removal of a single pronucleus from tripronuclear human oocytes and evaluate the future potential of this technique for obtaining diploid, transferable embryos.DesignLiterature review.SettingNone.Patient(s)None.Intervention(s)None.Main Outcome Measure(s)None.Result(s)Ten relevant studies were identified. These differ considering the removal technique itself, the application of cytoskeletal relaxants, and the survival rate after epronucleation. Diploidy and heteroparental inheritances could be confirmed in some preimplantation stages derived from epronucleated oocytes. Transfer of “corrected” embryos has been attempted only once, and resulted in a live birth. Noteworthy pitfalls associated with the procedure concern the exact identification of the supernumerary pronucleus, the presence of two centrosomes in dispermic oocytes, and cytogenetically abnormal pronuclear patterns after intracytoplasmic sperm injection.Conclusion(s)Patients with exclusively abnormally or few normally fertilized oocytes would profit from epronucleation to assure embryo transfer or increase the number of transferable embryos. Further research appears necessary and promising.