Laboratory and embryological aspects of hCG-primed in vitro maturation cycles for patients with polycystic ovaries

In this review, recent advances in the laboratory as well as embryological aspects of hCG priming in vitro maturation (IVM) cycles are described. This report is based on publications from literature searches and the authors' experience. In IVM cycles, priming with hCG permits the recovery of a certain number of oocytes with an expanding/dispersed cumulus pattern which facilitates its identification within follicular fluid as compared with non-primed IVM cycles. The immature oocytes with dispersed cumulus cells (CC) at collection have high IVM rates and embryo development potentials. Moreover, a few in vivo matured oocytes with dispersed CC can be obtained, and these have produced good quality embryos. hCG can be given to patients when a dominant follicle reaches 10-12 mm to avoid negative effects on the sibling immature oocytes. ICSI should be performed at least 1 h after the first polar body extrusion. Embryo transfer time depends on quantity and quality of the embryos produced after IVM. Compared with slow freezing, vitrification is a more efficient method for freezing the embryos produced from IVM. The data from the meta-analyses suggests that the effect on clinical outcome of gonadotrophin priming of IVM still needs to be studied. In order to improve the IVM programs, it is essential to define not only the clinical aspects but also the laboratory and embryological aspects.