Lactational amenorrhea is the temporary postnatal infertility that occurs when a woman is amenorrheic (not menstruating) and fully breastfeeding.
LAM method :
Lactational amenorrhea method is a natural method of birth control. In this breastfeeding delays the onset of menstruation in new mothers. Breastfeeding halts the release of hormone that triggers ovulation. Is is based on the fact that ovulation does not occur during the period of intense lactation following parturition.