Abstracts

One in six couples suffer from infertility, and many undergo treatment with in-vitro fertilization (IVF). Given that IVF often results in more embryos than can be transferred during one embryo transfer cryopreservation of the supernumerary embryos has been an important addition to IVF. In recent years, improvements in cryo-thaw technologies have increased interest in the transfer of frozen thawed embryos as a means of increasing the efficacy of the procedure and to encourage the transfer of fewer embryos, in order to reduce the costs and morbidity associated with multiple pregnancy. In the Netherlands, in 2015, over half of all embryos transferred was a frozen-thawed embryo. A key element of successful freeze thaw treatment is the appropriate preparation of the endometrium to receive embryos. In order to reach optimal synchronization of embryo and endometrium various methods of preparation have been developed. In the thesis Endometrial preparation methods in frozen-thawed embryo transferpregnancy and live birth rates of the various methods of endometrium preparation described in recent literature were compared. None of the methods of endometrium preparation methods could be preferred over another. Comparing the cost-efficiency of two of these methods of endometrial preparation methods similar conclusion were drawn. Therefore, the best method to prepare the womb for receiving a frozen and thawed embryo; it is up to the patient to decide. The second part of the thesis focusses on improving the efficiency of one of the methods of endometrium preparation. In so-called natural cycle frozen-thawed embryo transfer the patients own menstrual cycle determines planning of thawing and transferring. Various circumstances that might disrupt the synchronization between embryo and endometrium have been suggested. Insufficient endometrium thickness, elevated progesterone levels and the presence of an LH surge are suggested disruptors of endometrium embryo synchronization. Even though these circumstances are often observed during natural cycle frozen-thawed embryo transfer they seem to have little consequences with regard to pregnancy rates. Extensive hormonal monitoring also does not help identifying patients that will conceive from those that do not. From an efficiency point of view refraining from monitoring of various hormonal measurements and of the endometrial thickness can be considered.Advisors/Committee Members: Fauser, Bart, Macklon, Nicholas, Cohlen, B.J..