FACTBOX: Facts about U.S. work-family policies

(Reuters) - First lady Michelle Obama has said "helping working women balance career and family" will be one of her policy interests while her husband is president.

Following are some facts about working mothers and workplace policy in the United States, from official U.S. sources and academic studies:

* The United States is one of only four countries which does not have some form of paid leave for new mothers. The others are Papua New Guinea, Swaziland and Liberia.

* Under U.S. federal law, workers in companies with at least 50 employees can take six weeks unpaid leave after giving birth. Smaller companies are not required to offer any maternity leave, even unpaid.

* There are 82.8 million mothers in the United States; 72 percent of mothers are in the labor force.

* 81 percent of U.S. women aged 40 to 44 are mothers, down from 90 percent in 1976.

* Mothers are 79 percent less likely to be hired as non-mothers with identical resumes.

SOURCES: U.S. Census Bureau; The Institute for Health and Social Policy at McGill University; Shelley Correll, Stephen Benard & In Paik, Getting a Job: Is there a Motherhood Penalty, 112 The American Journal of Sociology 1297 (2007).

(Reporting by Andrea Hopkins, Editing by Frances Kerry)