In recent years, increasing attention and resources have been brought to bear on the relationship between the environment and congenital diseases. These diseases were previously thought to be mostly due to genetic causes. Even though the importance of genes as factors in causation is accepted, environmental factors seem to be implicated just as strongly. This book explores some further concepts that have arisen from more recent perceptions of environmental effects and their possible interactions with living systems. Amongst the topics discussed are:-effects of prenatal exposure to toxic chemicals-intra-uterine exposure to drugs-effects of endocrine disrupters-environmental risk and sex ratio in newborns-surveillance of environmental impact-research and policy. Discussion and presentation of old and novel ideas is targeted at developing a more holistic and united perception of the interaction between congenital diseases and the environment.