I had a recent visit with a provider, I had not seen in awhile. After our sexual encounter she noticed that she had started spotting. She was surprised that her her period had started 4-5 days early. A couple of girls have told me an orgasm during sex, sometimes triggers their menstrual cycle to start early. True or false.
Well, giddyup1979,
I've heard the same argument from some women. Theoretically, it would be the contractions of the uterus during orgasm that would facilitate the start of flow. On the other hand, the cycle itself is governed by the pituitary gland and various hormones and not simply contractions. Another factor is that when testosterone levels are up in women (when their estrogen and progesterone levels fall just before the period begins,) orgasm can be more easily facilitated.
So in one sense, contractions, if severe and persistent, can facilitate the beginning of flow; as to the cycle itself, no, they don't have any effect, since the cycle is governed by brain functions and not mechanical contractions.
Hope that makes sense,
The Love Goddess