[Oh geez. Sherlock had to know the differences between men and women... didn't he? He might profess to having no interest in sex in general and women in particular, but he had to have been given The Talk, right?]

Sherlock... er, I'm not so sure if it's the kind of thing the polyjuice potion replicates, but on the off chance that it is, you do know there are some biological functions women go through that men don't, right? Ones that require a pretty detailed idea of what to do to keep things from getting... messy.