Dr. Sebastiaan Mastenbroek is an Assistant Professor and one of the Clinical Embryologists of the Center for Reproductive Medicine of the Amsterdam UMC.

An important focus of his research has been Preimplantation Genetic Screening (PGS). Publication of his RCT on PGS in the New England Journal of Medicine started a fiercely debated controversy on the use of PGS as it showed that the technique actually lowered pregnancy rates after IVF instead of increasing them. He actively participated in this debate and published research that provided technical as well as biological reasons for the inefficacy of PGS.

In recent years his research focusses on early human development, improvement of human preimplantation embryo quality, assisted reproductive techniques, and evidence based laboratory practice. He supervised multiple randomized clinical trials. One of these trials demonstrated one embryo culture medium to be superior to another in terms of live birth rate after IVF, but it also demonstrated, for the first time by means of a large RCT, that there was a difference in birth weight of the children born after using these two media. He aims to find biological plausibility for the clinical outcomes of the trials. Like the transcriptome analysis of single embryos that demonstrated increased apoptosis pathways in the medium that resulted in less pregnancies. Furthermore, he aims to increase the basic understanding of human embryo development and implantation. His group demonstrated that high-quality human preimplantation embryos actively stimulate decidualized human endometrial stromal cell migration to increase their chances of successful implantation. They then identified the factor responsible for this newly discovered communication between embryo and endometrium.

He is a board member of the SAF foundation (stichting-saf.nl), chair of the LSFD laboratory working group, board member of the special interest group ART of the Dutch Society of Obstetrics and Gynaecology, board member of the Amsterdam Reproduction and Development Research Institute, associate editor of Human Reproduction Open, editor of the Cochrane Gynaecology and Fertility Group, and chair of the Science Committee of the Dutch Society for Clinical Embryology.

ORCID: orcid.org/0000-0002-7550-2924