The three essential criteria for the Lactational Amenorrhea Method of contraception (LAM) are:
1) baby less than 6 months old;
2) exclusive breastfeeding;
3) period has not returned.
Therefore, LAM cannot be relied upon once a woman's period has returned. However, if bleeding begins within a two-week interval after the bleeding from childbirth has stopped, it is not considered a period but rather an extension of postpartum lochia.