Among teenage girls living in U.S. cities, about half acquire at least one of three common sexually transmitted infections — chlamydia, gonorrhea or trichomoniasis — within two years of becoming sexually active, a new study has found.

The study of 381 girls, aged 14 to 17, also found that it was common for these patients to have repeated infections.

“Depending on the organism, within four to six months after treatment of the previous infection, a quarter of the women were re-infected with the same organism,” Wanzhu Tu, associate professor of medicine at the Indiana University School of Medicine and an investigator at the Regenstrief Institute, said in a university news release.

Subsequent sexually transmitted infections (not necessarily the same type) were diagnosed within two years after an initial sexually transmitted infection in about 75 percent of the girls, and within four years in 92 percent of the girls, according to the report in the December issue of the Archives of Pediatrics & Adolescent Medicine.

Tu and colleagues also found that screening for sexually transmitted infections may not begin until several years after a girl begins sexual activity, especially among those who become sexually active at a young age.

“This is important because many clinicians are reluctant to address sexual activity with younger teens, and may miss important prevention opportunities,” study senior author Dr. J. Dennis Fortenberry, a professor of pediatrics at the Indiana University School of Medicine, said in the news release.

Screening of sexually active teen girls should begin within a year after first intercourse and retesting of infected girls should be done every three to four months, the researchers said.