A new study by researchers at Johns Hopkins University shows that fulfilling unmet contraception demand by women in developing countries could reduce global maternal mortality by nearly a third, a potentially great improvement for one of the world's most vulnerable populations.

The study, published in The Lancet, a British science journal, comes ahead of a major family planning conference in London organized by the British government and the Bill and Melinda Gates Foundation that is an attempt to refocus attention on the issue. It has faded from the international agenda in recent years, overshadowed by efforts to combat AIDS and other infectious diseases, as well as by ideological battles.

The proportion of international population assistance funds that went to family planning fell to just 6 percent in 2008, down from 55 percent in 1995, while spending on H.I.V./AIDS represented 74 percent of the total in 2008, up from just 9 percent in 1995, according to Rachel Nugent, a professor of global health at the University of Washington, who cited figures from the United Nations Population Fund.

But population growth has continued to surge, with the United Nations estimating last year that the world's population, long expected to stabilize, will instead keep growing. Population experts warn that developing countries, particularly those in sub-Saharan Africa, where fertility continues to be high and shortages of food and water are worsening, will face deteriorating conditions if family sizes do not shrink.

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