If the lower abdomen and waist are not massaged during menstruation, clinically it will not affect the menstruation itself, such as the massage of limbs, trunk, hands and feet. If you massage the lower abdomen, it may stimulate the contraction of the uterus and cause menstrual blood to flow backwards. Clinically, menstrual blood contains endometrial debris, which may lead to endometriosis once it flows backwards into the pelvic cavity, which will clinically result in persistent and aggravated dysmenorrhea, and may also cause infertility. So you can massage during menstruation, but do not massage the lower abdomen, waist, on the menstruation itself will not be affected, so be sure to remind the massage therapist is in the menstrual period, to give attention.