Dec. 30 (HealthDay News) -- Teens who take virginity pledges are just as likely to have sex as teens who don't make such promises -- and they're less likely to practice safe sex to prevent disease or pregnancy, a new study finds.

"Previous studies found that pledgers were more likely to delay having sex than non-pledgers," said study author Janet E. Rosenbaum, a post doctoral fellow at the Johns Hopkins Bloomberg School of Public Health. "I used the same data as previous studies but a different statistical method."

This method allowed Rosenbaum to compare those who had taken a virginity pledge with similar teens who hadn't taken a pledge but were likely to delay having sex, she said. She added that she didn't include teens who were unlikely to take a pledge.

"Virginity pledgers and similar non-pledgers don't differ in the rates of vaginal, oral or anal sex or any other sexual behavior," Rosenbaum said. "Strikingly, pledgers are less likely than similar non-pledgers to use condoms and also less likely to use any form of birth control."

The findings were published in the January issue of the journal Pediatrics.

For the study, Rosenbaum collected data on 934 high school students who had never had sex or had taken a virginity pledge. The data came from the National Longitudinal Study of Adolescent Health.

Rosenbaum matched students who had taken a virginity pledge with those who hadn't. After five years of follow-up, those who had taken a pledge did not differ from teens who hadn't taken a pledge in rates of premarital sex, oral or anal sex, or sexually transmitted diseases.

Teens who had taken a pledge had 0.1 fewer sex partners during the past year, but the same number of partners overall as those who had not pledged. And pledgers started having sex at the same age as non-pledgers, Rosenbaum found.

The study also found that teens who took a virginity pledge were 10 percent less likely to use a condom and less likely to use any other form of birth control than their non-pledging counterparts.

"Sex education programs for teens who take pledges tend to be very negative and inaccurate about condom and birth control information," Rosenbaum said.

The study also found that, five years after taking a virginity pledge, more than 80 percent of pledgers denied ever making such a promise. "This high rate of disaffiliation may imply that nearly all virginity pledgers view pledges as nonbinding," Rosenbaum said.

She said teens who are religious tend to delay having sex, but that has nothing to do with virginity pledges or abstinence-only sex education programs.

Bill Albert, chief program officer for The National Campaign to Prevent Teen and Unplanned Pregnancy, said teens need to be encouraged to delay having sex, but they also need to be given the facts about safe sex.

"When pledgers fell off the wagon, they fell off hard," he said. "What have we gained if we encourage young people only to delay sex until they are older, but when they do become sexually active, they don't protect themselves or their partners?"

"The notion that it has to be either a virginity pledge or encouraging teens to have sex is a false dichotomy," Albert added. "There is a public consensus in this country to encourage teens to delay sex, but also provide them with information about contraception."

SOURCES: Janet E. Rosenbaum, Ph.D., postdoctoral fellow, Johns Hopkins Bloomberg School of Public Health, Baltimore; Bill Albert, chief program officer, The National Campaign to Prevent Teen and Unplanned Pregnancy, Washington, D.C.; January 2009, Pediatrics