Breastfeeding as birth control is known as the Lactation Amenorrhea Method (LAM), and was first set down on paper at the close of a meeting of lactation experts in Bellagio, Italy, in 1988. Referred to as the Bellagio Consensus, the report states, "A mother who is fully or nearly fully breastfeeding her infant and who remains amenorrheic [nonmenstruating] will have more than 98 percent protection from pregnancy in the first six months postpartum."(8)
Although the phrase "fully or nearly fully breastfeeding" remained undefined, the statement was based primarily on studies of breastfeeding women in Western cultures. And by Western standards, "fully breastfeeding" has been generally understood as breastfeeding on demand--implying an average of 8 to 12 feedings every 24 hours for the first month or two of life, gradually dropping off to 6 to 10 feedings. Also by Western standards, one or more night feedings is customary until about six months of age, and often much later.
The phrase "nearly fully breastfeeding" would similarly remain open to interpretation were it not for subsequent studies investigating the effects of supplementation on the pregnancy rates of breastfeeding women. These studies, including one that explored the introduction of solids at an average age of five months, reveal that supplementation, even on a daily basis, does not substantially reduce the contraceptive effectiveness of breastfeeding. In fact, over the first six months postpartum, supplementation is associated with a failure rate of only about 3 percent. The reason for such a low failure rate is twofold. First, although women who give supplementary bottles or solids are more likely to menstruate during the first six months postpartum, LAM requires that they begin using another method of contraception immediately after their first period. In addition, many women remain amenorrheic for several months after introducing solids.(9)