By DR. JENNIFER ASHTON, ABC News Senior Medical Contributor

If you have teenagers, you may or may not have already had the dreaded sex talk with them. And as awkward as they may be, new research shows those talks may actually have a positive impact.

Researchers examined 30 studies published over the last 20 years and found that teens whose parents enforced rules about dating and friends showed higher rates of delaying sexual activities as well as higher condom and other contraceptive use.

So what’s the best approach and how do you set realistic expectations?

First, be clear about your expectations. It’s great to be idealistic but be realistic, too.

And always let your teens know that they can come to you for advice, help or questions.

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