The study, published on Tuesday 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.

Maternal deaths fell to about 287,000 in 2010, the report said. The decline is attributable to increases in contraception and in antiretroviral drugs for mothers with AIDS, and to greater numbers of births attended by nurses, doctors or midwives with medical training.

The agencies said the deaths had fallen by 47 percent from the United Nations’ 1990 estimate of 543,000, but the organization has been revising its historical estimates in response to skeptical research by a rival group of epidemiologists at the University of Washington.