What causes menstruation not to occur?

Menstruation, the shedding of the uterine lining, occurs when a fertilized egg does not implant in the uterus. This is due to the hormonal changes that occur during the menstrual cycle. If a fertilized egg does implant, menstruation will not occur and pregnancy will begin.

Here are some of the reasons why menstruation may not occur:

- Pregnancy: This is the most common cause of missed menstruation. When a fertilized egg implants in the uterus, it will produce the hormone human chorionic gonadotropin (hCG), which prevents the shedding of the uterine lining.

- Hormonal imbalances: Hormonal imbalances, such as high levels of estrogen or low levels of progesterone, can also cause menstruation to be delayed or missed. This can be caused by a variety of factors, including stress, thyroid problems, and polycystic ovary syndrome (PCOS).

- Birth control: Some forms of birth control, such as oral contraceptives, can cause menstruation to be delayed or missed. This is because birth control prevents ovulation, which is necessary for menstruation to occur.

- Medical conditions: Certain medical conditions, such as uterine scarring, endometriosis, and cancer, can also cause menstruation to be delayed or missed.

- Eating disorders: Eating disorders, such as anorexia nervosa and bulimia nervosa, can also lead to missed or irregular periods due to hormonal imbalances and malnutrition.

If you are experiencing missed or irregular periods, it is important to see a doctor to rule out any underlying medical conditions.