The abortion rate has fallen to the lowest level ever recorded, even lower than before the Supreme Court's Roe v. Wade decision made abortion legal nationally in 1973, a new report finds.

The analysis by the Guttmacher Institute, a research center that supports abortion rights, attributes the trend mostly to better access to contraception and fewer unintended pregnancies. About 62 percent of the decline in the number of abortions in recent years occurred in the 28 states that did not have new abortion restrictions.

However, both the Guttmacher researchers and antiabortion groups believe the decline also reflects laws that have made it tougher for women to get abortions, and for clinics to continue to operate. According to the report, the number of abortion clinics nationwide fell from 839 in 2011 to 788 in 2014, or 6 percent.

As the Trump administration prepares to takes office, additional restrictions are being pushed at both the federal and state levels.

Americans United for Life spokeswoman Kristi Hamrick told NPR that laws such as those requiring women to view an ultrasound of their fetus before an abortion are "game changers, and we see the abortion rate dropping in response."

Joerg Dreweke, an author of the Guttmacher report, countered, "Rather than seeking to reduce abortion at all costs, policymakers should focus on facilitating women's access to the full range of contraceptive methods [and] ensuring their access to safe and affordable abortion care."

The actual number of abortions dropped to 926,200 in 2014, while the rate fell to just under 15 abortions per 1,000 women of childbearing age, according to the report.

The abortion rate peaked in the early 1980s and has been falling ever since, for reasons that have always been hotly debated.

Planned Parenthood president Cecile Richards told NPR that fewer women have needed abortions, especially in recent years, thanks to better access to contraception. The Affordable Care Act, or Obamacare,  requires insurance plans to cover all birth-control methods, including expensive long-acting methods, with no out-of-pocket costs to women.

"We're finally doing a better job of helping women get access to birth control that's affordable and that's high-quality," Richards said.

Republican leaders in Congress are working with President-elect Donald Trump to repeal Obamacare, as well as to halt federal funding for Planned Parenthood, even though the organization provides gynecological care to low-income women and cannot use federal funds to provide abortions.

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