I found this article interesting. It's based on a Reuters/Ipsos poll of women between the ages of 25 and 45. Instead of sub-grouping them by race, it asks whether they work and/or have children:
Childless working women favor Obama over Mitt Romney, the presumed Republican nominee, by a striking 20 points, 46 percent to 26 percent. "Obama has done pretty well, stimulating the economy, getting out of Iraq and investing in healthcare," said Joanna Giddens, 27, who works for a Denver nonprofit and can't afford health insurance.
Working mothers were less likely to favor the president, by 42 percent to 34 percent. Stay-at-home mothers such as Formato, along with unemployed mothers, gave the president only a 5-point margin: 37 percent to 32 percent.
What the groups have in common is that, so far, no more than three out of 10 of the women polled support Romney.