Excess prolactin may inhibit the menstrual cycle directly, by a suppressive effect on the ovary, or indirectly, by decreasing the release of GnRH.

Studies of U.S. and Scottish women show that at least six bouts per day and 60 minutes of suckling in a 24-hour period will typically sustain amenorrhea.

[4] When an infant suckles, sensory receptors in the nipple send a signal to the anterior pituitary gland in the brain, which secretes prolactin and oxytocin.

Now, however, it seems that this relationship is one of correlation not causation as prolactin levels in the blood plasma are simply an indicator of suckling frequency.

[5] Suckling as proxy indicator of infecundity rather than a direct, hormonal causal factor is supported in studies contrasting the nursing intensity hypothesis, which says that more intense (prolonged, frequent) breastfeeding will result in a longer period of lactational amenorrhea, and the metabolic load model, which posits that maternal energy availability will be the main factor determining postpartum amenorrhea and the timing of the return of ovarian function.

If net energy supply is high enough, a woman will resume ovarian cycling sooner despite still breastfeeding the current infant.

[6] Amenorrhea itself is not necessarily an indicator of infecundity, as the return of ovarian cycling is a gradual process and full fecundity may occur before or after first postpartum menses.

Additionally, spotting or the appearance of first postpartum menses can be a result of either lochia or estrogen withdrawal and not actual ovulation.

[8] In fact, it was found that among the Hutterites, more frequent bouts of nursing, in addition to maintenance of feeding in the night hours, led to longer lactational amenorrhea.

[9] An additional study that references this phenomenon cross-culturally was completed in the United Arab Emirates (UAE) and has similar findings.

[10] With regard to the use of breastfeeding as a form of contraception, most women who do not breastfeed will resume regular menstrual cycling within 1.5 to 2 months following parturition.

Overall, there are many factors including frequency of nursing, mother's age, parity, and introduction of supplemental foods into the infant's diet among others which can influence return of fecundity following pregnancy and childbirth and thus the contraceptive benefits of lactational amenorrhea are not always reliable but are evident and variable among women.

[11] For women who follow the suggestions and meet the criteria (listed below), lactational amenorrhea method (LAM) is >98% effective during the first six months postpartum.

There are multiple examples of LAM use covered in studies conducted about postpartum birth control methods in various countries and areas of the world.

[20] In Turkey, exploration of LAM has exposed a distinct lack of knowledge surrounding the connection between lactational amenorrhea and birth control.

This lack of knowledge is not necessarily evident in other parts of the globe as exemplified in South-Eastern Hungary with the use of post-partum contraceptives.