Experts say the finding shows that many young women aren't paying enough attention to the dangers of sexually transmitted infections (STIs), which condoms help prevent.
"We need to work on crafting a clear message about pregnancy prevention and STI prevention," Dr. Julia Potter, of the Boston Medical Center, and Dr. Karen Soren, of Columbia University Medical Center in New York City, wrote in a related editorial.
"Dual protection for sexually active adolescents should be encouraged, so that adolescents are not exposed to the risk of pregnancy or the risk of STIs as a result of selecting condom use vs. effective contraception use," they said.
The new study was led by Riley Steiner, of the U.S. Centers for Disease Control and Prevention, and appears March 14 in the journal JAMA Pediatrics.
Steiner's team noted that the use of long-acting methods of contraception -- intrauterine devices (IUDs) and implants such as Nexplanon -- is on the rise among teen girls. But at the same time, teens and young adults account for nearly 50 percent of all new STIs, the researchers said.
"There is a clear need for a concerted effort to improve condom use," among teen girls using long-acting contraception, they wrote.
In the study, Steiner's group tracked condom use among nearly 2,300 sexually active high school girls involved in the 2013 National Youth Risk Behavior Survey.
The researchers found that almost 2 percent of the girls used a long-acting reversible contraceptive and close to 6 percent used Depo-Provera injection, patch or ring. Meanwhile, slightly more than 22 percent of the teens were taking the Pill.
About 41 percent of all the girls surveyed said that condoms were used during sex, while about 12 percent said they resorted to the "withdrawal method" in an attempt to not get pregnant.
And the researchers found that girls who used long-acting contraceptives were more than 60 percent less likely to use condoms than girls who took the Pill.
Girls using any form of long-acting contraceptive were also more than twice as likely as those on either Depo-Provera or the Pill to have more than one recent sexual partner.
There was no difference in condom use among girls on long-acting contraception and those using Depo-Provera, the study found.
The researchers also noted that almost 16 percent of the girls did not use any form of birth control at all.
The bottom line, according to Potter and Soren, is that "condoms still need to be part of the [sexual health] conversation because STIs are common in the adolescent population. ... Condoms and [long-acting contraceptives] complement each other. We need to get the message right."More information
The U.S. Centers for Disease Control and Prevention provides more information on preventing sexually transmitted infections among teens .
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