Until recently, studies of the influence of nutrition on reproductive events such as the timing of puberty, the occurrence of ovulation in single-ovulating species and the actual numbers of ova shed in 'multiple ovulators' such as the pig and sheep dominated nutritional aspects of reproduction research. The emphasis is now switching to studies of the impact of nutrition during key periods of development in utero on subsequent production potential including reproduction. Already there is evidence that nutrition during early embryonic development can affect the foetal growth trajectories and size at birth. There are also data to indicate that nutrition during oogenesis not only affects ovulation rate but also embryo development and possibly the nature of the subsequent foetal growth and development processes. Coming at a time when functional genomics is capturing the attention of nutritionists, these observations are providing a unique and valuable opportunity to carry out research linking whole animal production responses with the underlying molecular and cellular biology. The present review describes a range of examples of the effects of dietary nutrients on gene expression during key periods of embryonic and foetal development. In doing so it illustrates the impact that nutrition in utero could have on improving animal production through its contribution to functional genomics.