The first thing to consider is that bleeding during ovulation, improper sex and other physiological factors, and the second thing to consider is endometriosis, cervicitis and other diseases. 1. Physiological factors: the entire menstrual cycle of women is divided into follicular phase, ovulation, luteal phase and menstrual period, ovulation, the female body hormone levels will drop significantly, resulting in the proliferation of endometrial shedding, some women will appear ovulation bleeding. At the same time, if a woman has recently had improper posture during intercourse, resulting in damage to the mucous membrane in the vagina, there will also be a lack of menstruation under the situation of light red blood. 2. Endometriosis: the specific cause of this disease is still unclear, clinical considerations are related to genetic factors, women’s menstrual blood reflux and other factors. This disease often leads to patients with dysmenorrhea, menstrual abnormalities, some patients will be manifested in the absence of menstruation under the light red blood. 3. Cervicitis: This disease is mainly caused by Neisseria gonorrhoeae, Chlamydia trachomatis and other pathogens, patients often appear leukorrhea discharge increase, abnormal vaginal bleeding and other symptoms, some patients may appear to menstruation did not come out of the bottom of the light red blood. There are many clinical reasons for the absence of menstruation, and it is recommended that patients consult a doctor in a timely manner to clarify the specific causes of the disease.