Women at Work
An early culprit was that fine new European institution, the University. Historically, many women had practised empirical medicine, but from 1271 the University of Paris insisted upon formal certification. By the early 1300s, women were being prosecuted for practicing medicine unlawfully. One example is Jacqueline Felicie de Alemania.
In Opera Muliebra, David Herlihy argues that women continued to be employed in many professions up until the population growth of the 1400s, after the great plague. In this century the power of the professional guilds was largely responsible for excluding women from apprenticeships.
The Church had tried to put women in their place for a millenium, without much success. The overriding factor in this story is that urban men wanted good work, once they had stopped fighting each other, and this was most easily achieved by excluding women, with excuses from Christian thought.