In Chapter 13, the predictions for Maha-Prajapati Biksuni and Yasodhara Biksuni come about in an indirect sort of way. The Buddha notices his aunt, the woman who raised him after his mother died in child birth, looking at him. I can just imagine it to be one of those looks only a mother could give a child, something on the order of a scolding without words. This would be a look that probably told the Buddha, hey aren’t you forgetting something.

At any rate the Buddha guesses what his aunt is thinking and asks her if she thought that somehow she had been left out of all the predictions that have now covered every practitioner type, Sravakas, Pratyekabuddhas, Bodhisattvas. He says he had already assured the Sravakas of their enlightenment and that he did not exclude her from that general grouping. In this I believe the Buddha realizes that even though he had implicitly included women in the general prediction, he realizes now that the women really need it clearly stated not just for them but for the males in the congregation.