He said that women should not be punished for taking time off when they are pregnant.
This is the part of Obama's speech that is interesting. (The 77% thing is just stupid and he should be called out on it.)
I think it might be fairer if women didn't face negative repercussions to their income for taking pregnancy-related time off. But I can't think of any good legislative solutions to the problem.
Requiring employers to pay women as if they never got pregnant doesn't really fix things. It doesn't help women who are self-employed, for example. If my neighbor and I are both self-employed women who play guitar at restaurants/bars for our income, how is the government going to ensure that I still make as much as my neighbor when I take a few months off from performing and she doesn't? Which restaurants/bars that I don't perform at are supposed to pay me?
Even for women who are employed by employers other than themselves, requiring employers to pay pregnant women for their time off may not be such a good idea. It will make women less employable. It's essentially making employers pay more per hour of work for women of childbearing age than for other employees, thus making other employees comparatively more attractive in the job market. That's not good for young women's employment prospects.
The best solution (which also comes up in discussions of minimum wage) may be to shift the burden from the employer to the government (i.e., to taxpayers in general). Allow the employer to give the pregnant woman unpaid time off, but have the government write her a check to cover any lost salary. That's just as good from a pregnant woman's perspective, and it removes some of the disincentive employers would otherwise have to hire women of childbearing age. (There's still the problem that a woman will miss out on work experience during her pregnancy leave, and that she'll have to be replaced temporarily, which involves transaction costs to the employer.)
But that last solution makes it look like the government is paying women to have babies, and moreover, it's paying high-income women a lot more than it's paying low-income women. Why would it do that? Are rich white babies worth more than poor black babies? There may be issues there . . .