Abstract

Human embryo implantation, the current rate-limiting step in ART, depends on
three essential elements: a competent embryo, a receptive endometrium and
an adequate synchronization between both. To this extent, the overarching
research question of this thesis was whether endometrial receptivity can be
optimized or predicted.
Follicular-phase endometrial scratching during ovarian stimulation followed by
a fresh embryo transfer did not increase the clinical pregnancy rate in a
truncated randomised study and may be harmful as a higher clinical
miscarriage rate was observed. A biomolecular study nested within this trial
did not reveal significant differential gene expression in relation to the clinical
outcome using transcriptome analysis of the whole-tissue endometrium, while
the secretome profile of isolated, cultured and in-vitro decidualized
endometrial stromal cells varied significantly between patients who had a live
birth compared to those with an implantation failure.
Genital tract microbiota research pointed out that ovarian stimulation
significantly influenced the cervical microbiota composition and diversity.
Furthermore, a DNA extraction protocol designed for low-biomass samples
allowed to increase intra-uterine microbiota profiles quality.
A randomised study in high-responders demonstrated that the freeze-all
strategy did not harm the pregnancy rates in comparison with a fresh embryo
transfer with an intensified luteal phase support, while it decreased the
patient’s risk to develop moderate-to-severe ovarian hyperstimulation
syndrome.
With regard to the frozen embryo transfer, retrospective data showed the lateproliferative
phase serum estradiol level not to be useful to guide clinical
decision-making in artificial cycles, while a randomized study in natural cycles
demonstrated the spontaneous and triggered ovulation approach to perform
comparably.
Date of Award15 Sep 2020
Original languageEnglish

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