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.

Pseudoephedrine: effects on milk production in women and estimation of infant exposure via breastmilk.

AIMS: To assess the effects of pseudoephedrine on breast blood flow, temperature and milk production, and to estimate the likely infant dose during breastfeeding. METHODS: Eight lactating women (mean age 35 years and weight 69 kg) participated in a single-blind randomized crossover study of 60 mg pseudoephedrine hydrochloride vs placebo. Breast blood flow and surface temperature were measured from 0 to 4 h following the dose, and change in plasma prolactin was measured as the difference between predose and 1 h postdose concentrations. Milk production was measured for 24 h following placebo and pseudoephedrine. Infant dose of pseudoephedrine for a 60-mg dose administered four times daily to the mother was quantified as the product of average steady-state drug concentration in milk and an estimated milk production rate of 0.15 l x kg(-1) x day(-1) and expressed relative to the maternal weight-adjusted dose. RESULTS: There were no physiologically significant changes in breast blood flow or temperature between the placebo and pseudoephedrine periods. The mean change in plasma prolactin was slightly (13.5%), but not significantly lower (t = 1.245, P = 0.253) after pseudoephedrine (1775 mU x l(-1)) compared with placebo (2014 mU x l(-1)). However, the mean milk volume was reduced by 24% from 784 ml x day(-1) in the placebo period to 623 ml x day(-1) in the pseudoephedrine period (difference between means 161 ml x day(-1) (95% CI: 63, 259 ml x day(-1)); t = 3.9, P = 0.006). Assuming maternal intake of 60 mg pseudoephedrine hydrochloride four times daily, the estimated infant dose of pseudoephedrine was 4.3% (95% CI, 3.2, 5.4%) of the weight-adjusted maternal dose. CONCLUSIONS: A single dose of pseudoephedrine significantly reduced milk production. This effect was not attributable to changes in blood flow, but depression of prolactin secretion may be a contributing factor. At the maximum recommended pseudoephedrine doses, the calculated infant dose delivered via milk was < 10% of the maternal dose, and is unlikely to affect the infant adversely. The ability of pseudoephedrine to suppress lactation suggests a novel use for the drug.