Blood Flow Characteristics of the Human Lactating Breast

Background: Despite the increased metabolic activity of the lactating breast, no studies have been carried out to determine mammary blood flow (MBF) parameters or the relationship between MBF and milk production in women. The aim of this study was to measure the MBF in the internal mammary artery (IMA) and lateral thoracic artery (LTA) of lactating women and determine if these were related to milk production. Methods: Blood flow in the IMA and LTA was measured with color Doppler ultrasound in 55 lactating women. Twenty-four-hour milk production was determined with the test-weigh method. Results: IMA contributed the greater proportion of blood flow to the lactating breast (70%). MBF was highly variable between women but consistent between the left (126 L/24 h; interquartile range, 76-169) and right (110 L/24 h) breasts. No relationship between MBF and milk production was demonstrated. For 3 women, MBF was markedly reduced in 1 breast that was synthesizing almost no milk compared to the other that was producing a normal volume of milk. Discussion: Although no relationship between MBF and milk production was found, the substantial reduction in blood flow in the breasts of lactating women producing almost no milk suggests a threshold below which milk production is compromised. Conclusion: Doppler ultrasound did not demonstrate a relationship between MBF and milk production in lactating women. Further investigation is required to fully understand the role of blood flow in milk synthesis.