Facebook chief operating officer Sheryl Sandberg says that until her husband's death, she never realised how hard it is to be a single parent.

She says in a touching Mother's Day weekend Facebook post that odds are stacked against single mums.

On Mother’s Day, we celebrate all moms. This year I am thinking especially of the many mothers across the country and...

Posted by Sheryl Sandberg on Friday, 6 May 2016

"For me, this is still a new and unfamiliar world. Before, 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," she writes.

"I did not understand how often I would look at my son's or daughter's crying face and not know how to stop the tears. How often situations would come up that Dave and I had never talked about and that I did not know how to handle on my own."

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She says many live in poverty, work two jobs or don't have paid leave to care for themselves or children if they get sick. She calls on leaders to rethink public and corporate work force policies to better support single mothers.

"For many single mothers, this is the only world they know. Each and every day they make sacrifices, push through barriers, and nurture beautiful families despite the demands on their time and energy.

"I realise how extremely fortunate I am not to face the financial burdens so many single mothers and widows face. Poverty is one of the hidden and devastating aftereffects of loss for women."

She says public and private policies need to be examined to make sure they "embrace and support and love" all families, no matter how they fit together.

Sandberg's husband, Dave, died in a treadmill accident a year ago while on vacation in Mexico.

- with AP