“Upward mobility is still not equal today,” said Muriel Pénicaud, chairwoman and chief executive of the Invest in France Agency and a former executive at Danone, the French food giant.

Daria Ostaptschuk had been in a diplomatic position with the O.E.C.D. in Paris when her child was born 10 years ago. When she returned to work part time, “my chances were not so good in advancing my career,” she said. “The trade-off is you are getting squeezed as a half-time worker, plus you don’t get the good jobs.” She now runs her own translation business.

The wage gap between men and women has shrunk in the United States and in a number of European countries since the mid-1990s. But it hasn’t budged in France — and has grown in Italy and Portugal.

Sometimes, cultural attitudes hold back working mothers. In Germany, labor market reforms in the 1990s led to more mothers entering the work force. But a cultural backlash rose in some corners against mothers who chose to spend time at work; a derogatory nickname — Rabenmutter, or “raven mothers” — was coined for those who pushed their children out of the house into day care.

Policy makers and employers in Europe and the United States seem to be making a calculation: Either keep a growing share of women employed or allow them good jobs and promising career paths. Neither seems to have figured out how to consistently do both.

There are signs that some American women, particularly college-educated ones, may be figuring out a new solution. They seem to be taking time out of the work force when they have children and returning when those children are older, according to data from Ms. Goldin at Harvard. That is certainly what many women would like to do. Of those women who are out of work and identify as homemakers in the Times/CBS/Kaiser poll, 67 percent said it was likely that they would be working five years from now.

Charlotte Mayo, 51, may be one of them. She left her job as a factory worker in her late 30s, when she began fertilization treatments. “I see a lot of middle-aged and older women becoming parents now, and they leave,” she said. She now stays home in Pomfret, Conn., with her 10-year-old twins, but said she would consider returning to work when they were older.

The plan is a gamble. Ms. Devine, the British mother who lives in Washington State with three children under 5 years old, would like to return to school to switch careers to a medical field like radiography when they are of school age. But she is pragmatic about it. “I don’t know if I’m hirable anymore,” she said, “because I’ve been out of the work force for so long.”