But that is indeed what they are doing: beating odds stacked against them. Most parents are simply not able to have it all, regardless of where they are on the income spectrum.

A recent study of business school graduates from the University of Chicago found that in the early years after graduating, men and women had “nearly identical labor incomes and weekly hours worked.” Men and women also paid a similar career price for taking off or working part time. Women, however, were vastly more likely to do so.

As a result, 15 years after graduation, the men were making about 75 percent more than the women. The study  done by Marianne Bertrand, Claudia Goldin and Lawrence Katz  did find one subgroup of women whose careers resembled those of men: women who had no children and never took time off.

On the other end of the spectrum, low-income women generally do not have a choice between career and family. Many are single parents. Their chances of escaping poverty are hurt by the long-term costs of taking time off after childbirth and having little flexibility in their schedules.

Taking the next step toward workplace equality probably has to start with an acknowledgment that most parents can’t have it all  at least as long as part-time work, flexible schedules and long leaves do so much career damage.

A growing number of parents already seem to have come to this conclusion. That’s one reason for the rise in the number of mothers who have dropped out of the labor force. Lacking good part-time job options, more are choosing full-time parenting.

Last year, 40.2 percent of married women with children under 3 years old were outside the labor force, up from a low of 38.6 percent in 1998. The increase, according to a Bureau of Labor Statistics analysis, “occurred across all educational levels and, for most groups, by about the same magnitude.” By contrast, women without children at home have continued to join the work force in growing numbers.