New research shows that the 2008–2011 abortion decline was driven by a steep drop in the unintended pregnancy rate, which in turn is most plausibly explained by improved contraceptive use. This new evidence has major implications for the U.S. abortion debate, argues a new Guttmacher Policy Review analysis. The findings not only affirm that contraceptive use is a highly effective way to reduce abortion incidence, but also strongly contradict explanations for the decline put forth by opponents of abortion rights.

A Guttmacher Institute study just published in the New England Journal of Medicine (NEJM) shows that the U.S. unintended pregnancy rate declined 18% between 2008 and 2011, to its lowest level in three decades. The NEJM study also finds a substantial drop in unplanned births and no change in the proportion of unintended pregnancies ending in abortion. The authors point out that contraceptive use improved during the same period.

“These findings provide significant new clarity for the U.S. abortion debate,” says Joerg Dreweke, author of the accompanying policy analysis. “We now know that abortion declined primarily because of fewer unintended pregnancies, and not because fewer women decided to end an unwanted pregnancy. Improved contraceptive use is likely the key driver of the decline.”

The analysis offers a detailed discussion of the new evidence and its implications for current policy debates, with three main takeaways:

Contraception as the key driver: Contraceptive use is likely the key driver of the 2008–2011 declines in unintended pregnancy and subsequent abortions. Overall use of contraceptives increased slightly among women at risk of unintended pregnancy between 2008 and 2012, while use of highly effective methods—such as the IUD and implant—more than tripled between 2007 and 2012. Research shows that the two-thirds of women who use contraceptives consistently and correctly account for only 5% of all unintended pregnancies.

Abortion restrictions and “culture of life” played no major role: There is now strong evidence that the 2008–2011 abortion decline was 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% in 2008, 42% in 2011), while the unplanned birth rate declined by 18%.

Uncertainty as to post-2011 trends: Data are insufficient to analyze post-2011 abortion trends and the underlying factors, although evidence suggests that the abortion rate continued to decline. 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.

“In short, supporting and expanding women’s access to family planning services not only protects their health and rights, it also reduces abortion rates,” says Dreweke. “The clear implication for policymakers who wish to see fewer abortions occur is to focus on making contraceptive care more available by increasing funding and stopping attacks on all family planning providers.”

Full Guttmacher Policy Review analysis: “New Clarity for the U.S. Abortion Debate: A Steep Drop in Unintended Pregnancy Is Driving Recent Abortion Declines,” by Joerg Dreweke

New England Journal of Medicine study: “Declines in Unintended Pregnancy in the United States, 2008–2011,” by Lawrence B. Finer and Mia R. Zolna.