A new study out of North Carolina suggests talking to your kids about sex does make them more likely to practise safe sex. This was most true if it was the mother who gave the talk, and daughters were more likely to benefit from the talk than sons.
http://archpedi.jamanetwork.com/article.aspx?articleid=2468098
https://www.nlm.nih.gov/medlineplus/news/fullstory_155469.html
http://time.com/4094495/alas-you-do-have-to-talk-to-your-teen-about-sex/
http://www.reuters.com/article/2015/11/02/us-health-parenting-teensex-idUSKCN0SR1U720151102
http://www.dailymail.co.uk/news/article-3301231/Mum-s-safe-sex-chat-DOES-work-Talking-birds-bees-teenagers-reduce-chance-risky-behaviour.html#ixzz3qTLtOsGJ