I have no idea, but my guess is that since there is much less $$$ at stake and the women get paid much less, they can't afford to dope, or at least no in sophisticated ways like the boys...
Well, Genevieve Jeanson admitted to doping... she was a pro roadie. Apparently, started EPO at 16. !!!! I would guess that because there is less money in it it would be less, too. Or at least the press hasn't gotten to it yet.