Metabolism plays a critical role in oocyte and early embryonic health, and much effort has gone into understanding the metabolic requirements for generation of ATP at these early stages of life. Special attention has rightly been placed on mitochondrial activity in energy production, as uniquely these early stages are associated with relatively immature mitochondria that display reduced efficiency in function. Oxygen and glucose levels are major metabolic players during early development, acting in other ways than just energy substrates fuelling ATP production. Over the past decade our laboratory has investigated the role of both oxygen and glucose participation in cellular signalling pathways, especially when either in excess and/or in restricted levels. Our work on oxygen levels has primarily involved the role of the Hypoxia Inducible Factor transcription family during development, where we have asked questions such as “is the large antral follicle hypoxic?” and “do early embryos transitioning from oviduct to uterus encounter hypoxic conditions?” In regard to levels of glucose, our work has focussed on hyperglycaemia in the reproductive tract impinging oocyte and early embryo development. It is well established that maternal diabetes reduces oocyte quality and embryo development, but the mechanisms involved are not established. Our focus has been characterising the changes in a protein post-translation modification, b-O-linked glycosylation, which is up-regulated in oocytes, early embryos and reproductive tract tissues under hyperglycaemic conditions. We have asked the question “how does this protein modification impact early development, and potentially, long-term outcomes and transgenerational health?” Studying oocytes and early embryo development has traditionally been possible only by ex vivo observations; recent involvement with large, transdisciplinary teams is bringing us closer to ask our questions within the in vivo environment, paving the way for a new understanding between early developmental events and the interactions these have with the maternal tract environment.