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DISCUSSION AND FUTURE PERSPECTIVE The biggest AHA advantages are to reach high implantation rates in some patients and recover pre-embryos with ZP abnormalities and excessive cytoplasmic fragmentation. It has been shown concomitantly that pre-embryos in hatching implant earlier than those ones having na intact ZP, which can cause a more intimate embryo-uterus synchronization relationship, during the implantation period. Patient’s immunesupression before transference of pre-embryos in hatching is a preventive measure that helps reduce the possible contact between uterus immune cells and the exposed pre-embryo. Pre-embryo fragmentation is one of the main factors in IVF failure. Fragmentation reduces the available cytoplasm for succesive blastomere divisions, and fragments having no nucleus can go through apoptosis, which is potentially harmful for viable blastomeres. Early fragment removal, for these reasons, help some embryos to manifest all its growth potential. Fragment removal attempts to imitate the natural process of apoptotic cell elimination by the immune system (apoptotic cell assisted removal), since pre-embryos and fragments express the apoptotic markers precociously in their cell membranes. These markers signalize, physiologically, their imminent removal. In reality, the role of apoptotic processes during the development of human pre-embryos needs to be better studied. The introduction of new techniques, like LASER and PIEZOMANIPULATION, have provided us with new and exciting directions for AHA. Piezomanipulation is especially promising, because it doesn’t involve exposition to chemical agents. Technical advances will propitiate improvement in the control of the size opened in the ZP and blastomere protection. AHA has been a success when aplied to pre-embryos with a poor implantation diagnosis, and can be combined with co-culture. However, a very small opening made in the ZP leads to na impairment in the natural process of hatching and possibly promotes the formation of monozygotic twins. On the other hand, if the opening is too large, it can cause blastomere loss during transference. AT solution, which has low pH, may have adverse effects on the blastomere viability if incorrectly manipulated. Finally, as human pre-embryos do not express polarization during compactation, the exact place in the ZP where natural hatching will occur cannot be identified. Consequently, the ideal place to perform the artificial opening, or even if there is any importance in choosing a place to pierce the embryo, must still be certified. The identification of embryos with best implantation probability will select the best embryos for AHA and transference. The death cause determination of the pre-embryo in vitro and the application of non invasive techniques to determine apoptotic blastomeres will allow their selective removal. The determination of pre-embryo viability using vital atoxic colorants and genetic markers will allow us to transfer only healthy embryos in the future, and thus enhance implantation rates. Concluding, AHA is no miraculous technique, although there is growing evidence of its benefit in specific cases. It is a very secure technique when used by na experienced embryologist. The AHA technique itself still presents controversies and different results in different centers, different AHA procedures and different experience levels.
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