Can a woman disclose her menstrual cycle to a non-Mahram, such as her future husband, without causing any wrongful thoughts in his mind?
Bismihi ta'ala
If there is a sensible reason why she informs a non-mahram when she is in her cycle, or when it starts/finishes, then there is no shar'i problem with that.
Muslim women usually conceal this information, because it is something private, and also out of modesty, but there could be times where she will need to disclose it, and there would be no issue with that.
And Allah knows best