There are two reasons why menstruation is delayed: 1, pregnancy, if you have sex after the last period is clean and do not do a good job of contraception, to rule out the possibility of unwanted pregnancy, generally more than 12 days after the last intercourse, you can use the test paper to test yourself, to rule out the possibility of unwanted pregnancy; 2, if you completely rule out pregnancy, it is likely to be caused by endocrine disorders. This cycle, if ovulation is abnormal, or even no ovulation, may also lead to delayed menstruation. Recent mental stress, irregular work schedule, frequent late nights, labor, irregular diet, change of environment, etc., may affect the ovulation of this cycle. Don’t be too nervous if your period is delayed once in a while, come to the hospital for an ultrasound to check the thickness of the lining of the uterus, and if necessary, take progesterone to bring your period on. If your period is often delayed or irregular, you must come to the hospital for an endocrine test to see what causes the delay, and then decide what to do next to regulate your menstruation.