(CNN) -- Contraception includes condoms and birth control pills, but there are other, longer-term methods that are effective and reversible: Intrauterine devices and implants.
A new study in the journal Obstetrics & Gynecology set out to see what would happen if these methods were given out at no cost. The study incorporated more than 9,000 girls and women at risk for unintended pregnancy.
Researchers found that teen births within the group of women who were part of this program was 6.3 per 1,000, which is much lower than the national rate of 34.1 per 1,000.
"We already spend $11 -- 12 billion on unintended pregnancies in the U.S., and I bet that money could go very far to provide contraception for many women in the U.S.," said Dr. Jeffrey Peipert, lead study author and researcher at Washington University in St. Louis School of Medicine.
Peipert and colleagues also found that the percentage of abortions that were repeat abortions was lower in this group of participants than in the St. Louis region in general, and the national average, during 2008 to 2010. The study intervention appeared to prevent one abortion for every 79 to 137 women who participated.
In previous research, Peipert and colleagues showed that these longer-term methods are as much as 20 times more effective than the birth control pill, the hormone patch and the hormonal vaginal ring. The long-acting options do not require the user to remember to take medications or change out a device, failings which can lead to unwanted pregnancies.
There are many barriers to the widespread use of long-acting reversible contraceptives in the United States, he said. One is the cost. One IUD costs a little over $700, not including the insertion fee, Peipert said, but it is very cost-effective given how long these devices last compared to other methods. The implant lasts three years, while the copper IUD lasts 10 years.
These longer-term options should be covered under insurance plans under the Affordable Care Act, although it remains controversial whether religious-based insurance carriers must provide contraception, Peipert said.
Another challenge is that clinicians are wary to give them to very young women, although they have been shown to be safe. Patients are also less aware that these methods exist.
Participants in the program were between 14 and 45 years old, did not want to get pregnant for at least 12 months, and planned to engage in sexual activity with a male partner within the next six months. About 5,000 participants received a free reversible contraceptive method for three years, while the rest got it for two years. Researchers used a variety of methods to enroll people in the study; 16% of the participants had been recruited at abortion facilities.
"Increasing access to the most effective contraceptive methods by removing cost and access as barriers has greatly increased the number of adolescents and women in the St. Louis region using the most effective methods of birth control," the study said.
There are limitations, however. This study was limited to a very specific demographic area, so it's hard to say how it would apply on a broader scale. Also, the study authors did not directly measure unintended pregnancies, but used measures of teen pregnancy and repeat abortions as a proxy.
The funding for the study came from the Susan Thompson Buffett Foundation. One of the study authors, Dr. Tessa Madden, is on the Speaker's Bureau for Bayer Pharmaceuticals; there were no other conflicts of interest reported. The Washington University Human Research Protection Office gave approval before recruitment.