A Google Groups member wonders if adding sexual health tips can affect your AdSense ad acceptance since Google will treat them as an "adult" site. The answer is yes, it can.
A casually written blog about someone's cooking lessons, for example, would probably be acceptable in the AdSense network, while a casually written blog about someone's personal sex tips probably wouldn't be acceptable.
More information can be see at the Google AdSense blog where they emphasize the importance of keeping the content allowed on AdSense "family safe."
The important statement that addresses the concern is here:
Our policy regarding adult or mature content may include any material that is not appropriate for all audiences. While this obviously includes full nudity or sexual activity, it may also include textually explicit sexual content, image or video content containing lewd or provocative poses, strategically covered nudity, see-through or sheer clothing, and close-ups of anatomy that would be inappropriate if shown nude. Additionally, topics such as sexual health and sex tips may be held to a higher standard of professionalism than content that isn't bordering on mature.
Forum discussion continues at Google Groups.