NEW YORK—Increased contraceptive use has led to fewer abortions worldwide, but deaths from unsafe abortion remain a severe problem, killing 70,000 women a year, a research institute reported Tuesday in a major global survey.

More than half the deaths, about 38,000, are in sub-Saharan Africa, which was singled out as the region with by far the lowest rates of contraceptive use and the highest rates of unintended pregnancies.

The report, three years in the making, was compiled by the New York-based Guttmacher Institute, which supports abortion rights and is a leading source of data on abortion-related trends. Researchers examined data from individual countries and multinational organizations.

The institute's president, Sharon Camp, said she was heartened by the overall trends since Guttmacher conducted a similar survey in 1999, yet expressed concern about the gap revealed in the new report.

"In almost all developed countries, abortion is safe and legal," she said. "But in much of the developing world, abortion remains highly restricted, and unsafe abortion is common and continues to damage women's health and threaten their survival."

The report calls for further easing of developing nations' abortion laws, a move criticized by Deirdre McQuade, a policy director with the U.S. Conference of Catholic Bishops' Secretariat for Pro-Life Activities.

"We need to be much more creative in assisting women with supportive services so they don't need to resort to the unnatural act of abortion," she said.

Guttmacher estimated previously that the number of abortions worldwide fell from 45.5 million in 1995 to 41.6 million in 2003 -- the latest year for which global figures were available.

A key reason for that drop, the new report said, was that the portion of married women using contraception increased from 54 percent in 1990 to 63 percent in 2003 as availability increased and social mores changed. Guttmacher's researchers said contraceptive use had increased in every major region, but still lagged badly in Africa -- used by only 28 percent of married women there, compared with at least 68 percent in other major regions.

The report notes that abortions worldwide are declining even as more countries liberalize their abortion laws. Since 1997, it said, only three countries -- Poland, Nicaragua and El Salvador -- substantially increased restrictions on abortion, while laws were eased significantly in 19 countries and regions, including Cambodia, Nepal and Mexico City.

Despite this trend, the report said 40 percent of the world's women live in countries with highly restrictive abortion laws, virtually all of them in the developing world. This category includes 92 percent of the women in Africa and 97 percent in Latin America, it said.