Abortion rates have plummeted in developed countries over the past three decades, new data published Wednesday in the Lancet with the Guttmacher Institute shows.

In the early 1990s, there were 45 abortions for every 1,000 women between ages 15 and 44. That figure has now dropped to 27 abortions per 1,000 women.

The decline spans from the United States and Canada across the Atlantic Ocean to European nations. It does not, however, hold true in developing African, Asian, and Latin American countries, where abortion rates have either held steady or slightly increased since the 1990s.

Abortion rates plummeting in Europe, North America

Abortion rate per 1,000 women ages 15 to 44

The declining abortion rates in the developed world, experts say, tell a story about better access to contraceptives. More frequent use of better birth control gives women more control over their fertility — and ultimately seems to lower abortion rates internationally.

"When contraceptives aren't available, women use abortion, even if it isn't legally sanctioned and even if it puts them at great physical risk," Diana Greene Foster, an associate professor at University of California San Francisco who studies abortion and contraception and has received the Lancet data, wrote in an email. "When contraceptives are more available, use of abortion declines."

Three key facts from the Lancet's big, new abortion study

The new Lancet data is one of the most comprehensive looks at international abortion data in recent years. It looks at trends in abortion rates as well as the demographics of who gets abortions. Here are a few of the most notable and surprising findings:

Countries where abortion is illegal don't have lower abortion rates. Lancet researchers looked at the legal status of abortion and found that it didn't correlate with lower abortion rates. Women were still terminating pregnancies despite the legal restrictions. This might reflect the fact that countries outlawing abortion also tend to have higher levels of women with unmet needs for birth control, which, the researchers say, "contributes to the incidence of abortion in countries with restrictive laws."

Lancet researchers looked at the legal status of abortion and found that it didn't correlate with lower abortion rates. Women were still terminating pregnancies despite the legal restrictions. This might reflect the fact that countries outlawing abortion also tend to have higher levels of women with unmet needs for birth control, which, the researchers say, "contributes to the incidence of abortion in countries with restrictive laws." Married women have higher abortion rates than unmarried women. The media often portrays the typical abortion patient as an unmarried woman who isn't ready to care for a child on her own. But that doesn't capture the demographics of abortion patients accurately. The Lancet data finds that married women generally have higher abortion rates. This is especially true in Europe, where the abortion rate for married women is more than twice as high as the abortion rate for unmarried women. North America, however, is an exception: Abortion rates here are slightly lower for married women.

The media often portrays the typical abortion patient as an unmarried woman who isn't ready to care for a child on her own. But that doesn't capture the demographics of abortion patients accurately. The Lancet data finds that married women generally have higher abortion rates. This is especially true in Europe, where the abortion rate for married women is more than twice as high as the abortion rate for unmarried women. North America, however, is an exception: Abortion rates here are slightly lower for married women. Abortion rates vary hugely by country. Caribbean countries currently have the highest abortion rates (65 per 1,000 women between 15 and 45). The lowest abortion rates are in North America (17 per 1,000 women) and Europe (18 per 1,000 women). Europe has experienced the sharpest decline in abortion rates, falling 79 percent since the early 1990s.

Better birth control, fewer abortions: explaining the developed world's abortion decline

The declining abortion rates are limited to the developed world. In developed countries, abortion rates appear to be either flat or rising.

Abortion rates per 1,000 women ages 15 to 44

One big differentiator between these countries seems to be access to contraceptives.

Modern birth control has become ubiquitous in developed countries. In the United States, for example, 99.1 percent of women who have had sex say they've used at least one contraceptive method — up from 94.8 percent in 1982. The United Nations has found that in most European countries, contraceptive use is well above 70 percent.

Birth control itself is getting better, too: Long-acting, reversible contraceptives like implants and modern IUDs have only come on the market over the past two decades. These contraceptives have failure rates below 1 percent — meaning that of 100 users, fewer than 1 will become pregnant. That's a huge improvement over condoms' 18 percent failure rate or even the birth control pill's 8 percent failure rate.

Access to these contraceptives has steadily increased in developed countries, making it easier to prevent pregnancy. But the same isn't true of developing countries, some of which have fewer than 20 percent of women in relationships using contraceptives.

UCSF's Greene Foster notes that there can be cultural obstacles even when contraceptives are available.

"In countries across the developing world, the most common reasons for not using a method of contraception are perceived low risk of pregnancy, a personal opposition to using contraception, and concerns about the health effects or side-effects of contraceptive use," she writes in a separate Lancet piece.

Addressing those types of concerns will likely prove key, then, to increasing contraceptive use in the areas of the world where rates still remain low.

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