What happens if the egg is not fertilised in woman ?

Explanation

Menstruation is the periodic event taking place after every 28 days in mature woman. This is a cyclic process, interrupted only by pregnancy. During menstruation there is bleeding through vaginal opening. The cell debris and unfertilised ovum is given out of the body during menstruation.
If the egg is not fertilised, it lives for about one day. Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a fertilised egg. Uterine lining becomes thick, spongy and richly supplied with blood. But if fertilisation does not occur then this lining is not needed any longer. So, the lining slowly breaks and comes out through the vaginal opening as blood and mucous.
This cycle takes place roughly every month and is called menstruation. It usually lasts for about two to eight days.