Natural methods of contraception are considered "natural" because they are not mechanical and not a result of hormone manipulation. Instead, these methods require that a man and woman not have sexual intercourse during the time when an egg is available to be fertilized by a sperm.
The fertility awareness methods (FAMs) are based upon knowing when a woman ovulates each month. In order to use a FAM, it is necessary to watch for the signs and symptoms that indicate ovulation has occurred or is about to occur.
References taken from:
http://www.medicinenet.com/natural_methods_of_birth_control/article.htm and
http://www.herbalmedicinesmanufacturer.com/
