What happens when menstruation is delayed for three days needs to be analyzed based on previous periods and other circumstances, and it is not possible to generalize. If your period was regular in the past, but suddenly your period is delayed for three days, and if you are a woman of childbearing age and have recently had sex without contraception, you need to consider whether there is a pregnancy situation, you can use a pregnancy test paper to test, or go to the gynecology department of the hospital to take a blood test. If pregnancy is ruled out, it is necessary to consider whether there is excessive stress, often late at night, or changes in the external environment, etc. It is also possible that the menstrual period is delayed for a short period of time. In general, menstruation advance or delayed within a week, are normal physiological conditions, do not need to worry too much, do not need special treatment, you can continue to observe. Before and after menstruation, women need to pay attention to keep warm, prohibit spicy, cold food, regular work and rest, avoid staying up late. In addition, you can not do strenuous exercise during menstruation, pay attention to menstrual hygiene, wash the vulva with warm water every day, and change sanitary napkins diligently.