If your period is delayed for 12 days and you are having normal sexual intercourse, you should first consider that you may be pregnant. It is recommended that you can buy early pregnancy test strips for testing, or you can go to the hospital for a blood HCG test, which is currently a more sensitive means of detecting pregnancy. If it is found that you are indeed pregnant, an ultrasound is performed to determine if the pregnancy is normal intrauterine. If the test does not reveal pregnancy, a possible delayed period needs to be considered depending on the situation. It is relatively normal that menstruation may be delayed by 1 week, but if it is 12 days late, pregnancy must be excluded. Of course, factors such as environment, mood or medication may also cause delayed menstruation and it is recommended to go to the hospital for examination and treatment as appropriate.