The report by three U.N. agencies and the World Bank found that maternal mortality declined at an average of less than 1 percent annually between 1990 and 2005. That is far below the 5.5 percent annual decline needed to achieve a U.N. goal of reducing the maternal mortality ratio by 75 percent by the year 2015, it said.
In 2005, the report estimated that 536,000 women died due to complications in pregnancy or childbirth, compared to 576,000 in 1990.
To achieve the Millennium Development Goal set by world leaders at a U.N. summit in 2000, the report said maternal mortality will have to decrease at a much faster rate, especially in sub-Saharan African, where the annual decline has been about 0.1 percent between 1990 and 2005.
"The realization of this goal will require increased attention to improved health care for women, including prevention of unplanned pregnancies and unsafe abortions and provision of high-quality pregnancy and delivery care, including emergency obstetric care," the report said.
The 48-page report, entitled "Maternal Mortality 2005," is based on estimates by the U.N. World Health Organization (WHO), the U.N. Children's Fund (UNICEF), the U.N. Population Fund (UNFPA) and the World Bank.
Commenting on the new estimates, Thoraya Ahmed Obaid, executive director of UNFPA, said: "In this 21st century no woman should die giving life. Millions of lives are at stake and we must act now."
"It is unacceptable that one woman dies every minute during pregnancy and childbirth when proven interventions exist ... to save women from dying," she said in a statement.
Obaid said "three simple interventions" are needed - skilled birth attendants, emergency obstetric care, and family planning.
In Africa, the report said, less than 50 percent of births are attended by a skilled health worker. That is far below the global target which aims to ensure that at least 90 percent of births worldwide are attended by skilled health personnel by 2015, it said.
Obaid said at the "Women Deliver" conference in London from Oct. 18-20, where 1,500 global leaders, health professionals and women's rights advocates are expected, "we will press all concerned to take unified action to improve the lives and health of women, mothers and newborn babies all over the world."
According to the report, of the estimated 536,000 maternal deaths worldwide in 2005, 270,000 occurred in the sub-Saharan Africa region alone, followed by South Asia with 188,000 - the two regions accounting for 86 percent of the total.
India had the highest number of deaths at 117,000 deaths, followed by Nigeria at 59,000, Congo at 32,000, Afghanistan at 26,000 and Bangladesh at 21,000, it said.
The report gives the estimated number of maternal deaths per 100,000 live births of 171 countries in 2005, and a "range of uncertainties" because of difficulties in compiling statistics.
The highest estimates were Sierra Leone at 2,100 deaths per 100,000 live births; Afghanistan and Niger at 1,800; Chad at 1,500; Somalia and Angola at 1,400; Rwanda at 1,300; Liberia at 1,200; Nigeria, Malawi, Guinea Bissau, Congo and Burundi at 1,100; and Cameroon at 1,000.
The lowest estimates were Ireland at 1 maternal death per 100,000 live births; Bosnia and Herzegovina, Denmark, Greece, Italy and Sweden at 3 deaths; Australia, Austria, the Czech Republic, Germany, Iceland, Israel, Kuwait and Spain at 4 deaths; and Switzerland at 5 deaths.
The estimate for the United States was 11 deaths per 100,000 live births, the same as Bulgaria and higher than most European countries, Japan, and New Zealand.
Among the regions, sub-Saharan Africa had the highest number of estimated maternal deaths per 100,000 live births - 900 in 2005. It was followed by South Asia at 490; Oceania, which includes Australia, New Zealand and many of the South Pacific islands, at 430; southeastern Asia at 300; western Asia and north Africa at 160; Latin America and the Caribbean at 130; Russia and other ex-Soviet states at 51; eastern Asia at 50; and developed regions at 9.
The probability that a 15-year-old girl will die from a complication related to pregnancy and childbirth during her lifetime is 1 in 26 in Africa compared to 1 in 7,300 in richer developed regions, the report said.