Accidental pregnancies have fallen by 18 percent in recent years, mostly due to better use of birth control, experts reported Wednesday.
A new study by the Guttmacher Institute finds the rate of unintended pregnancies dropped to the lowest level in 30 years between 2008 and 2011. "We suggest that the decline is likely due to increases in the use of contraception," the Guttmacher Institute, which studies reproductive health, said in a statement.
"Less than half (45 percent) of pregnancies were unintended in 2011, as compared with 51 percent in 2008," Guttmacher's Lawrence Finer and Mia Zolna write in their report, published in the New England Journal of Medicine.
"There were declines among women of all ages, incomes, and race and ethnicity groups. So the declines were seen across the board," Zolna told NBC News.
The United States has one of the highest rates of unintended pregnancy in the developed world. Before the latest findings, Guttmacher has said that by age 45, more than half of all American women will have had an unintended pregnancy, and three in 10 will have had an abortion.
Zolna and Finer found that 2.8 million of the 6.1 million pregnancies in 2011 were unintended. One reason the rate went down: women were more likely to use the most effective methods of birth control, known as long-acting reversible contraception.
"Use of these methods, especially the IUD, more than tripled between 2007 and 2012, from 3.7 percent of all contraceptive users to 11.6 percent," Guttmacher's Joerg Dreweke wrote in a policy analysis that accompanies the New England Journal of Medicine report.
The team also found that 42 percent of unintended pregnancies in 2011 ended in abortion, little changed from 40 percent in 2008. But because there were fewer accidental pregnancies, there were fewer abortions.
"The abortion decline between 2008 and 2011 was driven by a steep drop in unintended pregnancy, which in turn is most plausibly explained by more and better contraceptive use," Dreweke wrote.
"These findings have major implications for the U.S. abortion debate as, among other things, they validate that supporting and expanding women's access to contraceptive services leads to a lower incidence of abortion," he added.
"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."
Other recent reports show that the U.S. pregnancy rate has hit a record low.
The report came out the same day as the U.S. Supreme Court heard oral arguments in one of the biggest challenges in years to abortion rights. Clinics have been fighting a law in Texas that requires facilities that provide abortions to upgrade facilities, and for doctors to have admitting privileges at local hospitals.
Since the law was passed, the number of clinics providing abortion services in Texas dropped to 19 from 42. That number could fall to 10 if the Supreme Court upholds the law.
Federal health officials and medical groups such as the American College of Obstetricians and Gynecologists say U.S. women need better access to birth control and to medical care so they know how to use it.
"As women's health physicians, we fundamentally believe that in order to keep abortion safe, we must keep it both legal and accessible," ACOG president Dr. Mark DeFrancesco said in a statement.
"Without question, allowing state governments to impose restrictions that are not medically necessary will only make it harder for women to access the safe abortion care that they need. Barriers to care - under the guise of concerns about patient safety - are bad medicine."
The 2010 Affordable Care Act, known widely as Obamacare, requires health insurance companies to pay for birth control without charging customers. Finer hopes it will bring the rate of accidental pregnancies down even more.
"Our results predate the passage of the Affordable Care Act; our data is through 2011," Finer said.
"In other research that we have done since the passage of Obamacare we've seen that this has resulted in lower costs for women. Another key provision is that people under 26 can remain under their parent's health insurance plan until they are 26," he added.
"The period of 18 to 24 is a really high risk period for unintended pregnancy. The highest unintended pregnancy rates are for women in between the ages of 18 and 24. So we... could continue to see a decline in unintended pregnancy rate if in fact they translate into improved access to and use of contraception."