Teen mothers are much less likely to use condoms when they have long-acting contraceptive implants like intrauterine devices (IUDs) than peers using other types of birth control, a U.S. study suggests.

Correct and consistent condom use remains an important strategy for prevention of STIs and HIV, the researcher who led the study told Reuters Health.

Because long-acting contraceptives are so effective against preventing pregnancy, the American College of Obstetricians and Gynecologists (ACOG) recommends that new mothers of all ages be offered this type of birth control before they leave the hospital with a new baby. In a sign of success with this approach, increased use of IUDs and other forms of long-acting contraception have been linked to declining teen pregnancy and birth rates in the U.S.

One drawback of long-acting contraceptives, however, is that they don't protect against sexually transmitted infections, which have remained persistently common among teens. For this protection, teens still need to use condoms.

In the current study of 5,480 new teen mothers, only 29 percent used condoms. The young women who used long-acting contraception such as IUDs or hormonal implants under the skin of the arm were half as likely to use condoms as those not using long-acting birth control, the study also found.

"While teen birth rates in the U.S. are at a historic low, teens and young adults aged 15 to 24 years old account for more than half of new sexually transmitted infections (STIs) in the U.S. each year," said senior study author Lee Warner, chief of the Women's Health and Fertility Branch in the Division of Reproductive Health at the U.S. Centers for Disease Control and Prevention in Atlanta.

While STIs like chlamydia, gonorrhea and HIV affect people of all ages, they take a particularly heavy toll on young people, making condom use essential for this age group.

Treatments for chlamydia and gonorrhea can cure the infections, but when these infections go untreated, they can make it difficult or even impossible for women to get pregnant in the future. HIV is no longer an all-but-certain death sentence, but there is no cure and patients need lifelong treatment to control the disease.

Most of the teen mothers in the current study had not planned to conceive. They were typically 18 to 19 years old, unmarried and first-time mothers, according to the report in JAMA Pediatrics.

About 21 percent of them used IUDs after they had their babies and 17 percent used hormonal implants in the arm.

Teens with IUDs were the least likely to report using condoms, with only 15 percent saying they did, while 21 percent of young women with long-acting arm implants reported condom use.

Among those using shorter-acting contraceptive methods like hormonal patches, rings or injections, about 25 percent also used condoms, compared with 47 percent of pill users.

The study wasn't designed to prove whether or how different forms of contraception might directly influence condom use among teen mothers, and it also didn't explore how contraceptive choices impacted STI rates.

One limitation of the analysis is that researchers relied on survey responses from teens about condom use for pregnancy prevention - not for preventing STIs. It's possible that some teens said they didn't use condoms to prevent pregnancy because they were using another form of birth control for this purpose and only adding condoms to prevent STIs.

Some previous research has found no difference in condom use before and after women got IUDs, suggesting that this type of contraception may not necessarily change how well women protect themselves against STIs, said Dr. Tammy Chang of the Institute for Healthcare Policy and Innovation at the University of Michigan in Ann Arbor.

"In my opinion, the risks of multiple pregnancies GREATLY outweigh the risks of STIs," Chang, who wasn't involved in the study, said by email.

"Unintended pregnancy, especially among adolescents and young adults, is an event that dramatically changes every aspect of a young person's entire life forever," Chang said. "Most STIs can be tested for and treated, if not cured."

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