Both unintended pregnancies in the United States and the number of abortions have fallen, according to a new study from the Guttmacher Institute that calls the former decrease the "most plausible" explanation for the latter.

The study, published in the New England Journal of Medicine, said the unintended pregnancy rate dropped 18 percent between 2008 and 2011, to its lowest level in 30 years. Study authors Lawrence B. Finer and Mia R. Zolna, both of Guttmacher, noted, however, that close to half of all pregnancies still are unplanned.

Abortion opponents have suggested that new restrictions on abortion and more women deciding to carry their pregnancies to term are responsible for the decline in abortions. Others, like the Guttmacher Institute, an abortion-rights research organization, disagree on the driving force, instead crediting increased use of more effective and low-maintenance contraceptives.

But both sides agree that the resulting numbers are good news. "Unintended pregnancy is a key measure of the population's reproductive health and indicates the extent to which men and women can achieve their childbearing goals," said Zolna, who noted that one of the Department of Health and Human Services' Healthy People 2020 goals is reducing unintended pregnancies.

Using national data from several sources, Finer and Zolna said that the number of unintended pregnancies per 1,000 women ages 15 to 44 dropped from 54 in 2008 to 45 in 2011.

Finer emphasized that all categories of unintended pregnancies have been falling: "The pregnancies that end in abortion, the pregnancies that end in birth, the pregnancies that end in miscarriage. It's overall decline that is driving the drop in both abortion and unplanned birth," he said.

Unequal results

While researchers found there are fewer unintended pregnancies across demographic groups, including racial and ethnic backgrounds, education levels and income brackets, the Guttmacher report noted many disparities remain across those same categories. They noted that "unintended pregnancies remained most common among women and girls who were poor and those who were cohabiting."

There were clear disparities by race and education level, too. For example, poor women are five times more likely to have unintended pregnancies than wealthier women, said Zolna.

The "why" is harder to come by, said Finer, "though we have some thoughts about that. Our study wasn't designed specifically to ascertain why but we do hypothesize … that one of the main drivers in the decline is likely to be changes in contraceptive use." He said more women use contraception and that more effective methods have been developed.

Abortion declines

While there's broad agreement that abortion numbers have declined, there's broad disagreement on why that's true.

The National Right to Life's annual look at the state of abortion in America cites Centers for Disease Control and Prevention data also showing a decline. "The most recent CDC report, released in November 2015, found that in the 47 jurisdictions that volunteered data, there was a 4.2 percent drop in the number of abortions from 2011 to 2012," the group reported, heralding the declines as a demonstration of "pro-life progress."

In a Guttmacher Institute policy analysis, Joerg Dreweke wrote that between 2008 and 2011, the decline in abortions was likely "not the result of more women carrying unintended pregnancies to term because of state abortion restrictions or of their own accord, as abortion opponents have repeatedly argued. If this had been the case, fewer women who experienced an unintended pregnancy would have obtained an abortion and there would have been an increase in unplanned births. Neither of these happened during 2008-2011. Rather, the proportion of unintended pregnancies ending in abortion stayed stable (40 percent in 2008, 42 percent in 2011), while the unplanned birth rate declined by 18 percent."

Finer said no one's sure what a spate of laws intended to make abortions harder to obtain did to the numbers post-2011 — a time when more restrictions have been enacted by different states. There is insufficient data to tell.

"Other Guttmacher work has indicated that since that time there have been significant increases in abortion restrictions around the country, so it's possible that in the more recent period, abortion restrictions have had an impact on women's access to abortion," Finer said. "But our focus is on the 2008-2011 period and it indicates that declines in unplanned pregnancies are driving both the declines in abortion and in unplanned births."

Dreweke wrote that "it is likely that the surge in abortion restrictions that started in 2011 had a measurable impact in some states. It is also probable that unintended pregnancy declined further, including potentially as a result of the Affordable Care Act's expansion of insurance coverage overall and for contraceptive services in particular."

Finer told the Deseret News that one of the most effective ways to reduce abortion rates is to help men and women achieve their childbearing goals. Pregnancies that are planned and welcome are far less likely to result in abortion, he said.

Mirroring teen trend

The recent downward trend in unintended pregnancies among women of all child-bearing years is similar to what's been happening among teens for years.

"Teen pregnancy rates have been dropping like a stone," said Bill Albert, chief program officer of the national Campaign to Prevent Teen and Unplanned Pregnancy. "They are at historic lows and have been declining almost every single year since 1990."

Teen births are down 61 percent from their peak in the early 1990s, he said.

Those older than teens, however, have not had similar declines in unplanned pregnancies, according to Albert, until recently. "After a considerable lull where unplanned pregnancy rates remained stable," he said, the decline is good news for both those who oppose abortion and those who want women to have the choice. "Not surprising, unplanned pregnancies are at the root of all abortions," said Albert.

He discounts any claims that more teens have elected abortions, thus driving unplanned births down. "We have seen simultaneous declines in pregnancy, birth and abortions," he said, giving credit to teens for "clearly making better decisions," including less sexual activity and better contraception.

Research also suggests that in the last few years, teenagers are waiting longer to have sex.

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