Oocytes are essential in maternal reproduction as they can be considered immature ‘gg cells’ The fate of an oocyte is to become fertilized and ultimately to grow into a fully functioning organism. This competence seems to be affected by the maternal micro-environment, the follicular fluid, in which oocytes develop. In this respect, increased levels of non-esterified fatty acids in the follicular environment of both high yielding dairy cattle as well as (overweight) women have been suggested to similarly contribute to increasing problems of infertility. This study relies on a vast and unique amount of samples from two distinct experimental designs (a controlled dietary intervention study and a cohort study). Fatty acid determination after separation in lipid classes, as proposed within the current project, will result in the generation of a particularly unconventional set of data which will support progression beyond the state of the art. The results of this comparison will provide novel information on the selective distribution of fatty acids among different lipid classes into fluid compartments. These insights will allow to assess the potential and limitations of nutritional interventions to improve fertility.