Specifically it sounds like it happens when she comes. Should I warn him there might be a problem? To quote the nice doctors on medicine. Although the cause of fainting is often something benign, it is not normal. And there are a good many possible causes and related factors.

Fainting after an orgasm can be scary. In most cases, it is not the orgasm itself that causes a person to faint, but the circumstances surrounding it. Low blood sugar, intense sex, fatigue, and even anxiety may trigger fainting. People who pass out after an orgasm usually do not need to worry.

I just heard that a woman can faint while having an orgasm. If so, is this normal? What causes this? While this is not the norm, there are some logical explanations. As people become sexually aroused, their breath shortens and quickens.