A study showed that teens who thought their parents were not aware of what they were up to when boyfriends or girlfriends sleep over are more likely to engage in unprotected sex. Based on this, is it advisable then for parents to discuss safe sex and other issues concerning sex with their teenage kids? The concern of most parents is if they do this, they’re afraid it may be construed as a license to engage in sex. However, the repercussions of having teenagers who engage in unprotected sex can seem to outweigh the concern of having sex early.
http://www.nytimes.com/2011/08/01/opinion/american-attitudes-toward-teenage-sex.html?_r=1