https://support.google.com/youtube/answer/2802002

Explicit content meant to be sexually gratifying is not allowed on YouTube. Posting pornography may result in content removal or channel termination. Videos containing fetish content will be removed or age-restricted. In most cases, violent, graphic, or humiliating fetishes are not allowed on YouTube.

We may allow nudity when the primary purpose is educational, documentary, scientific, or artistic, and it isn’t gratuitous. For example, a documentary on breast cancer would be appropriate, but posting clips out of context to sexually gratify from the same documentary is not. Out of context nudity in indigenous communities, during medical procedures, during childbirth, during artistic performances, or during breastfeeding may not meet our documentary exception. The same applies to depictions of sex scenes in artistic content such as films, audio stories, music or video games. Remember that giving context in the content, title, and description will help us and your viewers determine the primary purpose of the video.