PhD defence E.S. (Eva) van Marion

Below is a brief summary of the dissertation:

IVF (in vitro fertilization) success rates have improved, but selecting the best embryo remains challenging. Many seemingly high-quality embryos still fail to implant. It is essential to understand which factors from the gametes contribute to embryo quality and to identify other predictive factors to improve embryo selection. This dissertation investigates female and male factors that contribute to pre-implantation embryo development and identifies potential predictive factors for IVF success.
There are differences in development speed between embryos from testicular and ejaculated sperm. Embryos from testicular sperm have a longer first cell cycle and more frequently divide directly from one to three cells. On an epigenetic level, a higher H3K9me3/H3 ratio correlates with a longer interval between the fading of pronuclei and the first cleavage division, affecting embryo development but not significantly impacting pregnancy outcomes.
Time-lapse incubation provides extensive data for embryo selection. Predictive models developed in this dissertation forecast pregnancy chances based on development speed and the woman's age. These models assist in deciding between transferring a single embryo or a double embryo transfer, balancing pregnancy chances with avoiding twin pregnancies. Additionally, larger and faster-expanding blastocysts have a higher likelihood of successful pregnancy, which is a potential predictive factor.
Finally, this dissertation shows that couples from low socioeconomic status (SES) neighborhoods have a lower cumulative ongoing pregnancy rate after IVF treatment compared to those from high SES neighborhoods, despite equal access to fertility care in the Netherlands.