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Vitrification of day 5/6 human morulas/blastocysts: A 10 year retrospective study in a private assisted reproductive techniques [ART] clinic

Wilson Poe, Emma (2015-03)

Thesis (MMed)--Stellenbosch University, 2015.


ENGLISH ABSTRACT: This study was designed to retrospectively evaluate the established embryo vitrification/warming programme currently implemented at Drs Aevitas Institute for Reproductive Medicine and to look at factors that might play a role in optimizing the pregnancy outcomes thereof. Vitrification is the achievement of a “state of suspended animation” wherein molecular translational motions are arrested without structural reorganization of the liquid. In embryo vitrification it involves placement of the embryo in a very small volume of vitrification medium that must be cooled at extremely high cooling rates. The vitrification medium contains cryoprotectants to prevent any cryoinjury from occurring to the embryo. This process was initially proposed to effectively manage supernumerary embryos, but it has also provided a viable method of reducing costs for additional embryo transfers as well as the reduction of the incidence of multiple births. Patients who are at risk of ovarian hyper stimulation syndrome (OHSS) can also have all of their embryos vitrified in advance to reduce the likelihood of adverse clinical symptoms if a pregnancy is established. Throughout the period in which vitrification has been in practice, there have been advances in technology as well as continual research being conducted to establish whether newly suggested techniques do, in fact, optimize the outcomes of vitrification. Focus has subsequently been applied to the carrier device used for vitrification, the day on which the embryos are vitrified and stored, as well as the number of embryos transferred in each respective cycle, all to ensure the most favourable outcome. This retrospective study confirmed the use of the Cryotop® as the most viable carrier device for successful survival and pregnancy outcomes. Transfer of day 5 vitrified embryos resulted in significantly higher pregnancy rates compared to day 6 vitrified embryos. Results also indicated that the number of embryos transferred does indeed have a significant effect on the pregnancy outcome and consequently we can possibly argue against the implementation of single embryo transfer in the vitrification programme. Investigation into the effect of female age, specifically oocyte age, on each of these categories indicated that reduced age can be associated with optimal outcomes; however this could not be proven statistically in this cohort of patients. To further look at optimization of the vitrification/warming programme, a Literature Survey was conducted to ascertain the results after Assisted Hatching in frozen/warmed human embryos. Assisted Hatching has been proposed as a solution to Zona Pellucida hardening, which has been found to occur during vitrification. The need for further studies and a meta-analysis of the literature is confidently proposed, as well as a Prospective Study to evaluate the effect of Laser Assisted Hatching in the human blastocyst vitrification/warming programme at Drs Aevitas Institute for Reproductive Medicine.

AFRIKAANSE OPSOMMING: Hierdie studie is ontwerp om die gevestigde embrio vitrifikasie/ontdooi program by Drs Aevitas Instituut vir Reproduktiewe Medisyne, retrospektief te evalueer en die faktore te optimaliseer wat swangerskap uitkomste kan beïnvloed. Vitrifikasie is die proses waardeur die molekulere aktiwiteit binne die embrio in ‘n staat van arres gehou word sonder om die strukture binne die sitplasma te versteur. Dit behels die plasing van ʼn embrio in 'n klein hoeveelheid vitrifikasie medium wat teen 'n hoë tempo afgekoel word. Die vitrifikasie medium bevat kriobeskermmiddels wat die embrio tydens die vitrifikasie proses teen moontlike skade beskerm. Hierdie proses is aanvanklik voorgestel om oortollige embrio’s doeltreffend te bestuur. Dit bied ʼn koste effektiewe metode vir embrio terugplasing, en verlaag die insidensie van veelvoudige swangerskap. Vitrifikasie bied pasiënte met ʼn hoë risiko vir ovariale hiperstimulasiesindroom (OHSS) ‘n alternatief om nadelige kliniese simptome te vermy indien ʼn swangerskap bereik word. Tegnologiese vordering en voortdurende navorsing ondersoek voortdurend nuwe tegnieke vitrifikasie uitkomste te optimaliseer. Fokus word geplaas op die draertoestel wat gebruik word vir vitrifikasie, die dag waarop die embrio's gevitrifiseer en gestoor word, sowel as die aantal embrio’s wat met elke vitrifikasie siklus teruggeplaas word. Hierdie retrospektiewe studie het bevestig dat die gebruik van die Cryotop® die mees suksesvolle toestel vir oorlewing en swangerskap uitkomste is. Die terugplasing van dag 5 gevitrifiseerde embrios het beduidende hoër swangerskapsyfers as dag 6 embrios tot gevolg gehad. Die resultate het ook aangedui dat die aantal embrio's wat teruggeplaas word 'n beduidende uitwerking op die swangerskapsyfer het. Daar kan dus moontlik teen die implementering van 'n enkel embrio-terugplasing neiging in die vitrifikasie program geargumenteer word. Resultate het ook getoon dat optimale uitkomste verwant is aan ʼn laer oösiet ouderdom, alhoewel dit nie in die groep pasiente statisties bewys kon word nie. 'n Literatuurstudie oor AH (Assisted Hatching) op gevitrifiseerde/ontdooide menslike embrio’s is uitgevoer om die vitrifikasie/ontdooi program verder te optimaliseer. AH bied ‘n oplossing vir Zona pellucida verharding, wat tydens vitrifikasie plaasvind. Verdere studies, 'n meta-analise van die literatuur, sowel as 'n prospektiewe studie om die effek van laser AH in gevitrifiseerde/ontdooide menslike blastosiste by Drs Aevitas Instituut vir reproduktiewe medisyne te evalueer, word voorgestel.

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