Experts couldn't say whether more liberal laws led to fewer procedures, but said good access to birth control in those countries resulted in fewer unwanted pregnancies.
The global abortion rate remained virtually unchanged from 2003 to 2008, at about 28 abortions per 1,000 women aged 15 to 44, a total of about 43.8 million abortions, according to the study. The rate had previously been dropping since 1995.
About 47,000 women died from unsafe abortions in 2008, and another 8.5 million women had serious medical complications. Almost all unsafe abortions were in developing countries, where family planning and contraceptive programs have mostly levelled off.
"An abortion is actually a very simple and safe procedure," said Gilda Sedgh, a senior researcher at the U.S.-based Guttmacher Institute, designated by the World Health Organization as an official Collaborating Center for Reproductive Health. "All of these deaths and complications are easily avoidable," said Sedgh, the study's lead author.
Sedgh and colleagues concluded that the proportion of unsafe abortions rose from 44 per cent in 1995 to 49 per cent in 2008, the last year for which statistics were available and studied in the report. Sedgh acknowledged it was difficult to get an accurate number for unsafe abortions in particular and described their estimates as modest.
They used sources including official statistics, national surveys, and hospital records. To account for unreported abortions, they made adjustments and relied on information from other kinds of studies, expert assessments, and surveys of women.
The research was published Thursday in the journal, Lancet.
Abortion rates were lowest in Western Europe — 12 per 1,000 — and highest in Eastern Europe — 43 per 1,000. The rate in North America was 19 per 1,000. Sedgh said she and colleagues found a link between higher abortion rates and regions with more restrictive legislation, such as in Latin America and Africa. They also found that 95 to 97 per cent of abortions in those regions were unsafe.
The authors defined unsafe abortion as any procedure done by people lacking needed skills or in places that don't meet minimal medical standards. Sedgh said some women in Africa resort to using broken soda bottles or taking strong doses of medicines or herbal drugs to induce abortions.
"It is precisely where abortion is illegal that it must become safer," wrote Beverly Winikoff and Wendy R. Sheldon of the Gynuity Health Projects in New York, in an accompanying commentary.
Experts said increasing birth control options for women in poor countries, like providing long-acting implants, would make a big difference.
"Wherever we have made better contraception available in the countries where we work, hundreds of women will walk hours to get it," said Dana Hovig, CEO of Marie Stopes International, a family planning organization. He was not connected to the study.