There are probably around 1,000 intersex babies born every year in the United States. The numbers can add up. The term actually refers to six different conditions where children are born with ambiguous sexual structures.
The majority are the result of something going wrong early in a pregnancy, where the fetus is exposed to an inappropriate amount of hormones in the uterus.
You can get genetic girls who look from the outside like males because they were exposed to male hormones at a critical stage of fetal development. Conversely, you can get genetic males looking like females because they didn't get enough male hormones in utero.
There are a whole group of more mixed external manifestations of gender that also occur.
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