Actually, prevalence of transsexual women (the accepted term for what you meant, since "women" is what they identify as) is probably quite a bit higher than that. http://ai.eecs.umich.edu/people/conway/TS/TSprevalence.html does an analysis that concludes that said prevalence is on the order of 1 in 500.

But I don't think we were talking about transsexuality, which is something different from the intersex conditions which might make this whole business of sex testing more complicated than one might expect.