Sex development occurs in stages. Babies have many opportunities to develop along paths that are not the typical one male or female phenotype. When sex development follows a less common path, the result is a difference of sex development (DSD*). Knowing at what point the path changed helps us provide appropriate medical care.
*DSD is a term in evolution. Commonly used terms to describe DSD conditions include difference of sex development, disorder of sex development and intersex.
Differences of sex development occur more frequently than most people realize. An estimated one in 4,500 children has such a condition. While many times, these differences are found at birth, some are not found until later in life, even though these conditions are present since early in development.
Human development is a complicated process. Slight differences in the usual process can result in a difference of sex development. Because these developmental differences occur before birth, they are called congenital.