He’s a she, and she’s a he, and sometimes it’s hard to determine. A fair number of kids are born with ambiguous sex characteristics due a variety of causes, ranging from nondisjunction events to hormone use by the mom. Caught up in the screening for athletes who cheat by using steroids, are the people who naturally have characteristics of both sexes, chromosomally, hormonally or externally.
Interestingly only those athletes performing as female have been screened. (Maybe the male athletes competing in shooting matches, for example, also be screened since women are naturally better shots.)
Some of the past Olympic athletes of ambiguous sex are enumerated in this story .
Note that the term sex is used here, to denote the usual human dimorphism, (and rare polymorphism) , rather than gender, which is a social or a grammatical term.