Suddenly stopping menstruation for a day may be a symptom of pregnancy, or it may be caused by irregular menstruation. 1. Pregnancy: Women who are pregnant basically do not have menstrual periods, but if there is a pre-miscarriage or ectopic pregnancy, it may lead to bleeding symptoms, which can be mistaken for menstruation. 2. Irregular menstruation: If a woman has irregular menstruation, it may lead to a decrease in the amount of menstruation and a shortening of the duration of menstruation, so the symptoms of menstruation may appear on the day of menstruation and suddenly stop. Normally, you need to observe your personal physical condition, if you find irregular menstruation, it is recommended to actively seek medical treatment to determine whether there is pregnancy. If irregular menstruation occurs, it needs to be treated under the guidance of a doctor.