The world's richest countries guarantee mothers more than a year of paid maternity leave. The U.S. guarantees them nothing.

Twenty-five years ago President Bill Clinton signed the Family and Medical Leave Act, which included a provision giving eligible workers 12 weeks of unpaid leave to care for a new child. Emphasis on "unpaid."

The United States remains the only country in the developed world that does not mandate employers offer paid leave for new mothers, according to the Organization for Economic Cooperation and Development.

New mothers in Finland, for instance, are entitled to up to three years wor...