PhD defence J. (Jeffrey) Hoek

Dissertation in short:

The periconception period is defined as the period 14 weeks before conception and 10 weeks thereafter. Within this period, all developmental stages essential for successful
fertilization and pregnancy course take place. Examples of these biological developments are spermatogenesis, oogenesis, pre- and postimplantation embryonic development,
implantation and placentation. A diversity of maternal and paternal factors can influence the course of these processes, such as genetics and epigenetics. Also nutrition and
lifestyle factors are involved, which determine the health of the biological surroundings of the developing pregnancy. The one-carbon (1-C) metabolism is essential in all of the
developmental stages since it provides 1-C moieties for various biological processes in order to successfully accomplish optimal embryonic, fetal and placental growth and development. A lot of research is performed to investigate the association between maternal effects of the 1-C metabolism on pregnancy outcomes. The most well-known example is the maternal preconceptional folic acid supplement use, or a folate rich dietary pattern, lowering the risk of neural tube defects in developing embryos during pregnancy. Far less research is performed investigating the association and effects between paternal nutrition and lifestyle factors on early embryo development, pregnancy course and outcome.

Couples suffering from subfertility can accomplish a pregnancy using artificial reproductive technologies. By spontaneous or assisted fertilization of an oocyte by sperm in the
laboratory, an embryo is created. Early development of these embryos before transfer to the uterus of the future mother can be studied. This allows for investigation of paternal,
and also maternal, effects on embryonic development. Subsequent surplus embryos can be cryopreserved for later use. The use of these artificial techniques, including assisted
fertilization, growth in culture medium, freezing followed by thawing, can all potentially induce (epi) genetic differences in the embryonic genome.

The goal of the current thesis was to investigate the effects of parental nutritional and lifestyle and in vitro conditions in relation with (preimplantation) embryo and placental
development.