Think about it: hold demand for goods and services constant (after all, women, while not working, were still eating and wearing clothes) and then suddenly double the available workforce (i.e. women start going to work.)

And while some women may be forced to work, and don't want to, there are a number of women who delay childrearing because of their careers. Women who have children later in life have fewer children on average. Additionally, some women choose to not raise children at all; if they didn't have the choice to work they would have to marry and have children so they wouldn't starve to death.