Between 1990 and 2014, an average of 56 million abortions took place each year worldwide, reported the study, published in the medical journal The Lancet.
The stubbornly high rate of abortions in poorer countries highlights an urgent need for better access to modern contraception, including the pill, implants and IUDs, the researchers said.
“In developing countries family planning services do not seem to be keeping up with the increasing desire for smaller families,” explained lead author Gilda Sedgh from the Guttmacher Institute in New York.
“More than 80 percent of unintended pregnancies are experienced by women with an unmet need for modern methods of contraception, and many unwanted pregnancies end in abortion.”
The study, done in collaboration with the World Health Organization, also concluded that restrictive laws do not curtail the number of abortions.
Indeed, in countries where ending pregnancies is broadly restricted — and thus frequently performed under unsafe conditions — the incidence of abortion was estimated to be as high as in countries where it is legal.
During the 25-year period under review, the annual abortion rate in developed nations per 1000 women 15 to 44 years old dropped from 46 to 27.
This was in large part due to a sharp reduction in Eastern Europe, where the rate fell by more than half as modern contraceptive methods became widely available.
In the developing world, however, the abortion rate remained virtually the same, declining from 39 to 37 per thousand women.
Besides Eastern Europe, rates also fell in southern Europe (from 38 to 26), Northern Europe (22 to 18), and North America (25 to 17).
The overall abortion rate in Africa — where the vast majority of abortions are illegal — increased slightly in 2014 compared to the preceeding 24 years to 34 abortions per 1000 women of child bearing age.
“The obvious interpretation is that criminalising abortion does not prevent it but, rather, drives women to seek illegal services or methods,” Diana Greene Foster, a professor at the University of California in San Francisco, said in a comment, also in The Lancet.
Lack of access to contraceptives where abortion is illegal often results in unintended pregnancy and unsafe abortions, she said.
“Such women face an increased risk of maternal mortality, and bear children that they are not ready to care for and often cannot afford,” she added.