Data from the Luxembourg Income Study show that, among married or cohabiting mothers, better educated women are more likely to be employed; gender inequality in annual earnings is thus less extreme among the well educated than among those with less education, driven largely by educated women's higher employment.
Another factor affecting which women are employed is the cost of childcare. If mothers, rather than fathers, are the ones responsible for care, then the benefits of a woman's job have to outweigh her childcare costs in order for it to make economic sense that she take the job. Given this cost-benefit analysis, highly educated women are more likely to be employed than less educated women because they can earn more, net of childcare costs. Note, however, that childcare costs cannot be the only factor affecting women's employment: if it were, we would not expect an educational gradient on employment in countries that provide large subsidies for childcare.