The global mortality rate for women giving birth has fallen by half over the past two decades, a U.N. report released Wednesday 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 per cent 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 per cent since 1990.

Sub-Saharan Africa accounted for 56 per cent of the deaths and southern Asia another 29 per cent, totalling 85 per cent of the global tally of maternal deaths in 2010. Two countries accounted for a third of global maternal deaths: India at 19 per cent and Nigeria at 14 per cent, it said.

Canada had less than 20 maternal deaths per 100,000 live births, the lowest category on the report's map.

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

The United States did not rank in the top tier of countries in terms of maternal health, falling behind Western Europe, Canada and Australia, and ranking on a par with Russia, Central and South America and parts of north Africa, it found.

Deaths among women giving birth were 15 times higher than in developed countries, said the report, titled "Trends In Maternal Mortality: 1990 - 2010."

The report defined maternal death as occurring during pregnancy or within 42 days of termination of pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes.