Breast Development and Control of Milk Synthesis

Abstract

We have developed a computerized breast measurement system that can quantitate both long-term (lactation cycle) and short-term (between breastfeedings) changes in breast volume. The increase in breast volume during pregnancy was not related to milk production at one month of lactation, whereas milk production from one to six months of lactation remained constant and was not controlled directly by the suckling-evoked secretion of prolactin. From the measurement of circadian changes in breast volume, it was concluded that infants rarely emptied the breasts at a single breastfeeding and that short-term variation in the rate of synthesis during the day and between the left and right breasts was closely related to the degree of breast fullness. Furthermore, differences between women in the storage capacity of the breasts dictated their flexibility in frequency of breastfeeding. These observations are consistent with the autocrine (local) control of milk synthesis during established lactation in women.