What changes occur in the uterus if fertilization does not occur?
OR
What happens to the human egg if fertilization does not occur?

Explanation

Every month, the uterus prepares itself to receive a fertilised egg. Therefore, the inner lining of the uterus becomes thick and is supplied with blood to nourish the embryo. If the egg is not fertilised, then the lining of the uterus breaks down and gets released in the form of blood through the vagina. This lasts for about two to eight days. This cycle occurs every month and is known as the menstrual cycle.