About 50 per cent of the girls under trial in Indianapolis were found to contract a sexually transmitted disease within two years of becoming sexually active and the remaining got infected within four years.

HealthDay News reported that researchers from the Indiana University School of Medicine were all ears on identifying chlamydia, gonorrhea or trichomoniasis that are three of the more common STDs in 381 girls put under trial.

The study reported that many girls had their partner use a condom but not every time they had sex. In some cases, Fortenberry said, girls may stop having their partner use a condom after they achieved a comfort level. The findings were that they also may stop using a condom at all.

The researchers, led by Wanzhu Tu of the Regenstrief Institute, indicated that STD testing in sexually active girls should begin within one year of intercourse. The test should be done three to four times a year.

An international charity aimed at educating the public about STDs called AVERT reported that chlamydia cases increased since 2001 by more than 40 per cent.

Dr. J. Dennis Fortenberry, IU professor of pediatrics and a senior author of the study said, "With little sexual experience they are exposed to these infections more."

The above study and other research stated that their was a need to educate teens sooner about the risks of sexual activity, said Elizabeth Schroeder, executive director of Answer, a Rutgers University-based sex-education group.