The global mortality rate for women giving birth has fallen by half over the past two decades, a U.N. report released said.

While there has been considerable progress, more work remains because a woman dies of pregnancy-related complications every two minutes, the report said.

The report from the World Health Organization, United Nations Children's Fund, United Nations Population Fund and the World Bank said about 99 percent of maternal deaths occur in developing nations, and most are preventable. It said there were an estimated 287,000 maternal deaths in 2010, a decline of 47 percent since 1990.

Sub-Saharan Africa accounted for 56 percent of the deaths and southern Asia another 29 percent. Two countries accounted for a third of global maternal deaths: India at 19 percent and Nigeria at 14 percent.

The United States had 21 maternal deaths per 100,000 live births, a total of 880 maternal deaths in 2010, the report said. U.S. maternal deaths rose an average of 2.5 percent a year from 1990 to 2010.

--ASSOCIATED PRESS