Mammalian reproduction is a complex phenomenon. Human fertility is highly impacted from environmental exposure to toxicants as well as nutrients. The burden of environmental stimuli is heavy and multifaceted. The contaminant sources are many, often occult, and at present, the wide range of positive and negative consequences on the ecosystem and the human health is only partially understood. Compounds deriving from industrial manufacturing, pesticides, waste accumulation and burning are only some examples of the contaminants daily impacting human life. Ovary and testis biology, primordial germinal cells and gametogenesis are primary targets of a large number of pollutants. Pregnancy holds the basis of the healthy post-natal life of each individual and his offspring. During the pre-natal development, genetic and epigenetic factors concur to determine the good sequence of events for the good final outcome of the pregnancy. Worldwide epidemiological studies and focused experiments in animal models are unraveling the molecular basis of the normal and abnormal development. Evidences are growing about the relationship between pregnancy conditions and the onset of metabolic and other complex diseases in adult life. Epigenetic mechanisms, including DNA methylation, histone marks and non coding RNAs, are main molecular players of normal development and of the adaptive response during pre- and post-natal life.