



It never specifies in the Lore or Fluff depending on how you prefer it, that the Vostroyans d not employ females in their units. As a code the rule imposed on them due to their treachery during the Horus heresy "All first born sons must join the Imperial guard". However this is not to say that the Regiment only employs Males, rather the opposite, if the only recruits from the world they send are first born males the current divisions out on duty would quickly deplete and it would be a few years before they could send out another full strength force of first born and so through logic it would suggest that other men are also enrolled into the ranks of the guard and also by that argument any women who wish to join are unlikely to be turned away.You also have to take into consideration who GW caters its product for, they tend to be men or boys who usually want to play or read about the great acts of men in war as opposed to women.