Many teenagers and young adults do not use contraception as often as they report, new research suggests.
Scientists at Emory University carried out a study of 715 black women and girls between the ages of 15 and 21 in which they asked them how many times in the past two weeks they had sex and how many times they had used a condom.
A total of 186 women reported having sex during the two-week period and using a condom every time.
However, analysis of vaginal fluid samples revealed that 34 per cent of these women had Y chromosome DNA in their fluid samples, indicating the presence of sperm.
The researchers believe that some women may have incorrectly assumed their partner had used a condom, while others may have experienced a contraceptive malfunction or simply been too embarrassed to admit they had not used protection.
Writing in the Archives of Pediatrics and Adolescent Medicine, they point out that "regardless of whether the problem is condom user error or misreporting, the unfortunate result, in terms of risk for [sexually transmitted infections] and HIV, is the same", Reuters Health reports.
According to the Family Planning Association, condoms are 98 per cent effective when used according to instructions.
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