Oocyte vitrification: efficiency and safety in an oocyte donation programme

Student thesis: Doctoral Thesis


At the start of this thesis in 2008, oocyte vitrification just grew out of its
infancy. Since the first report of a pregnancy from a frozen-thawed human
oocyte in 1986, many efforts were made to improve the efficiency of the
cryopreservation protocol, for both slow-freezing and vitrification. It was
only in 2005 that an efficient and reproducible protocol was described with
the use of an open vitrification device. However, national guidelines have
encouraged the use of closed devices in order to prevent crosscontamination.
The present thesis aimed (i) to optimize the efficiency of an
oocyte vitrification protocol with the use of a closed vitrification device and
(ii) to test the safety of the developed protocol.
By analysing different warming rates, it appeared that a high warming rate
is necessary to obtain high survival rates and developmental competence up
to the blastocyst stage. Also, gradual or direct exposure to cryoprotective
agents was analysed, showing that both methods can be successfully applied
on oocytes. After a successful protocol was obtained with a closed
vitrification device, this protocol was compared on oocytes vitrified with an
open device, generating much higher cooling rates. Though the survival rate
was not different between the open and closed device, it appeared that the
embryological development is faster when oocytes are vitrified with an open
device. Concerning the safety; the chromosomal meiotic constitution,
developmental kinetics and DNA (hydroxy)methylation were compared
between fresh and vitrified sibling donor oocytes and showed comparable
results. Finally, obstetric and neonatal data from all oocyte donation cycles
performed with the use of a closed vitrification device were retrospectively
analysed and are similar to other reports after oocyte vitrification.
Date of Award20 Dec 2016
Original languageEnglish
Awarding Institution
  • Vrije Universiteit Brussel
SupervisorHilde Van De Velde (Promotor), Greta Verheyen (Promotor), Dominic Stoop (Promotor), Mieke Geens (Jury), Dorien Van Saen (Jury), Michel De Vos (Jury), Giovanni Coticchio (Jury), Martine Nijs (Jury) & Ingrid Van der Auwera (Jury)


  • Oocyte vitrification
  • pregnancy

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