Prenatal environmental influences on the production of sex-specific traits in mammals

The determination of offspring sex represents a delicate balancing act during which offspring must pass through several developmental levels in the presence of influential environmental factors. Successful expression of sex-specific traits requires genetic and hormone-based effects on several organizational and activational levels. Environmental factors can exert controls and disruptions at each of these levels. This review addresses the developmental stages at which environmental factors may influence the processes of sex determination, with an in depth focus on the prenatal stages, including the production of the primary and secondary sex ratios and the differentiation of functional secondary sexual characters.