A new study headed by the World Health Organization (WHO) and Guttmacher Institute has revealed that abortion rates have significantly dropped over the past 25 years to historic lows - but only in wealthy countries. In poorer, developing nations, numbers have only slightly dropped. The data also suggests that restrictive laws on abortion do little to lower abortion rates and instead are more likely to force people to use unsafe methods for termination.

The findings shed light on the lack of access to proper contraception methods in poorer countries. These methods, such as the pill, implants and coils, make it more difficult to avoid unwanted pregnancies.

"In developing countries ... family planning services do not seem to be keeping up with the increasing desire for smaller families," said Gilda Sedgh, who led the research at the Guttmacher Institute in the U.S.

Using data from nationally representative surveys, official statistics and various published and unpublished studies, the researchers used a statistical model to estimate the trends in abortion incidence for all major areas of the world between the years 1990 and 2014.

The results reveal that during this time period, the annual abortion rate in the developing world dropped from 46 per 1,000 women of childbearing age (15 to 44 years) to just 27. Furthermore, this decrease is largely due to the major rate decrease in Eastern Europe stemming from the increased availability of modern contraceptive methods. Conversely, abortion rates in poorer countries dropped from 39 to 37.

In addition, the study shows that abortion rates in countries where the procedure is illegal are very similar to countries where it is legal, with 37 abortions per 1,000 women in countries where it is prohibited or only allowed to save a woman's life, compared to 34 per 1,000 where it is legal.

"More women living in countries with the most restrictive abortion laws have an unmet need for contraception - that is, they want to avoid getting pregnant but are not using a method of family planning - than women in countries with more liberal laws, and this adds to the incidence of abortion in countries with restrictive laws," Sedgh said.

The findings were published in the May 11 issue of the journal The Lancet.