There are two main reasons for delayed menstruation: 1. Pregnancy-related menopause needs to be ruled out, and pregnancy-related factors can be ruled out by monitoring the blood or urine HCG. The body secretes a special hormone called chorionic gonadotropin (HCG for short) after pregnancy, which doubles as the number of days of menopause increases, so monitoring the blood or urine HCG can qualitatively determine whether it is pregnancy. 2. The most common factor is the delayed menstruation due to endocrine disorder. The thickness of the endometrium can be determined by ultrasound monitoring and a progesterone withdrawal test can be performed after pregnancy is ruled out.