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Facebook Chief Operating Officer Sheryl Sandberg has made an impassioned plea on behalf of single mothers, in the run-up to Mother's Day.

, Ms Sandberg said the odds were stacked against single parents in the US.

She called on the government to introduce paid maternity leave.

Friday's appeal comes a year after the executive's husband, Silicon Valley entrepreneur Dave Goldberg, died in an accident in Mexico.

Since then, Ms Sandberg has raised the couple's two children on her own, as well as continuing to work for Facebook and running the women's support group Lean In.

She said that, before her husband died, "I did not quite get it. I did not really get how hard it is to succeed at work when you are overwhelmed at home."

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She said she was fortunate not to have to face the poverty that many single parents were burdened with, and the "impossible choices" resulting from such things as illness and food insecurity.

She said the US was the world's only developed economy that did not provide paid maternity leave, and that large numbers of single mothers had no safety net.

"Almost a third of working mothers don't have access to any kind of paid leave to care for themselves or their families if someone gets sick," she said.

"Instead of providing support, we all too often leave the families who are struggling the most to fend for themselves.

"The odds are stacked against single mothers in this country. Yet so many give everything they have and go on to raise incredible children."

In the past, some critics have suggested that Ms Sandberg's Lean In philosophy, advocating a pro-active attitude in the workplace, was irrelevant to most women because they lacked her resources and her social position.

But US media commentators said her admission that she had not previously understood the difficulties of single parenthood was significant.

"Well, duh, you might say, and Sandberg understands how you might have that exasperated reaction," writes , citing the fact that her loss was cushioned by her wealth and support network.

"But this is precisely Sandberg's goal," Marcus adds, "to leverage her atypical platform to bring heightened attention and understanding to hurdles faced by single mothers lacking her resources."