Lactational amenorrhea method (LAM) is the practice of relying on breast feeding as birth control. This method is considered 98-99% effective as long as a woman is not menstruating, is regularly breast feeding, and has a baby less than 6 months old. If any of those three criteria change, it is advised that another method of contraception be adopted.
More About Lactational Amenorrhea Method (LAM)
The name for this method comes from the words "lactation" (or producing milk) and amenorrhea (the absence of menstruation). LAM is considered by many to be ineffective often due to knowledge of someone who became pregnant while breast feeding. However, it is often a lack of understanding the three key criteria that causes pregnancy in women practicing LAM.