NEW YORK (CNN) -- Developing countries where abortion is outlawed can be the most dangerous places in the world to terminate pregnancies, a comparative study released Thursday has found.

It drew links between death rates of women undergoing abortions and the development level of they country where they underwent the procedure

The study found that although abortion rates were similar in rich and poor countries, the mortality rates due to complications from the procedure were higher in the developing nations.

Thirty-nine out of every 1,000 women of childbearing age have abortions each year in developed countries, compared to 34 per 1,000 in developing countries, said the study by The Alan Guttmacher Institute, a research group that receives some funding from the abortion rights group, Planned Parenthood.

"The fact that the rate is that high in the developing world, where abortion is illegal, and therefore expensive or unsafe, it indicates to us how motivated women are" to seek abortions, said Susheela Singh, the institute's director of research.

"They seem to find a way, even when there's a risk," Singh said.

In developing countries that outlaw abortion or where it is widely unavailable, the mortality rate from complications is far higher than in developed nations -- an average of 330 deaths per 100,000 abortions compared with between 0.2 and 1.2 per 100,000.

In Africa, an estimated 680 of every 100,000 women who undergo an abortion die of complications, researchers said. In Canada, which has one of the lowest abortion death rates, the study said there were 0.1 deaths per 100,000 abortions.

Overall, 38 percent of the estimated 210 million pregnancies that occur worldwide each year are unintentional; 22 percent end in abortion.

Worldwide, about 35 of every 1,000 women of childbearing age -- 3.5 percent -- have abortions each year, the report said. About 26 million women have legal abortions each year, and about 20 million have illegal abortions.

Researchers attributed the high rates of unplanned pregnancy and abortion worldwide to inadequate availability and use of contraception.

"It really points to the difficulties that women and couples have in planning their pregnancies," said Susan Tew, a spokeswoman for the Guttmacher Institute.

Eastern Europe had the highest rate of unplanned pregnancies and the highest abortion rate of any area of the world: 90 abortions per 1,000 women of childbearing age, the study said. Western Europe had the lowest abortion rate, 11 per 1,000 women, although its abortion laws are similar to those in Eastern Europe.

Researchers said the disparity could be because of the greater availability and use of contraceptives in the West.

Twenty-three percent of all U.S. pregnancies end in abortion, the new study said.

The study found that 30 percent of all pregnancies in Africa were unplanned, as were 39 percent in eastern Asia (excluding Japan), 34 percent in the rest of Asia, 52 percent in Latin America, 63 percent in Eastern Europe, 33 percent in the rest of Europe and 45 percent in North America, Australia, New Zealand and Japan.

Researchers compiled statistics from surveys in 65 countries and used World Health Organization estimates for countries in which data was unavailable. They collected data on unplanned pregnancy from 49 countries and used local surveys to estimate rates for countries in which complete information was unavailable.

Worldwide abortion and unplanned pregnancy figures from previous years were unavailable, so it was difficult to say whether rates were rising or falling, Tew said.

The Associated Press contributed to this report.