About half as many women worldwide die from pregnancy, childbirth and related complications compared with two decades ago, according to United Nations estimates released Wednesday.

The declining numbers of maternal deaths -- from 543,000 in 1990 to 287,000 worldwide as of two years ago -- were cheered by the World Health Organization, the United Nations Population Fund, UNICEF and the World Bank, which jointly issued the report.

But a global goal of reducing maternal deaths by 75% from 1990 to 2015 remains distant in some countries where progress has been slow or nonexistent.

"We can’t stop here. Our work must continue to make every pregnancy wanted and every childbirth safe," U.N. Population Fund executive director Babatunde Osotimehin said.

Women whose deaths are linked to pregnancy or childbirth most commonly lose their lives to severe bleeding, infections, high blood pressure during pregnancy and unsafe abortions, the report said.

The report credited the increasing percentage of women who had skilled medical workers on hand during their pregnancy and childbirth, increased access to therapies for HIV-positive women giving birth, and more contraception use for the decline in deaths. The greatest strides were in eastern Asia, where the rate of maternal deaths dropped nearly 70% from 1990 to 2010.

But the problem remains grave in many parts of the world, particularly central and western Africa. Almost all maternal deaths occur in developing countries, with more than half occurring in sub-Saharan Africa.

The number of deaths rose in about one of seven countries analyzed in the report, including Chad, Somalia and Zimbabwe.

In the United States, the maternal mortality rate went up by almost two-thirds, putting it behind Western Europe, Canada and Australia and alongside Iran, Hungary and Turkey. The actual numbers, however, are still low compared with many other countries, going from 12 maternal deaths per 100,000 live births to 21 per 100,000.

The shaded map below, included in the U.N. report, shows the number of women who died per 100,000 live births as of two years ago, the most recent worldwide data available:





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-- Emily Alpert in Los Angeles

Photo: A newborn holds his mother's hand at the intensive-care unit of the Marie Curie children's hospital in Bucharest, Romania, on March 18. Credit: Vadim Ghirda / Associated Press