Milk ejection patterns: an intra- individual comparison of breastfeeding and pumping.

BACKGROUND: Milk ejection is a transient episode critical to milk removal and women typically have multiple milk ejections during breastfeeding and pumping. Recently it was found that milk ejection characteristics such as number of milk ejections and periodicity were consistent throughout 12 months of lactation in women who expressed their milk with an electric breast pump. It is not known whether the stimulation of an infant at the breast influences milk ejection patterns or whether this is a programmed event. The aim of this study was to compare milk ejection patterns during breastfeeding and expressing milk with an electric pump within mothers. METHODS: Twelve lactating mothers with normal milk production (502-1356 mL) had milk ejection recorded by measuring the diameter of a major milk duct with ultrasound imaging throughout an entire breastfeed and a 15-min pumping session. Scans were analysed for timing, duration of duct dilation and maximum duct diameter. RESULTS: The initial milk ejection defined as the first increase in duct diameter was observed earlier during breastfeeding than during two phase pumping sessions but was not statistically significant (p = .057). There were no significant differences between the duration of the first or second milk ejection for mothers when breastfeeding or pumping at their maximum comfortable vacuum (p = .18; p = .99). The times taken to reach the peak duct diameter, or the first half of the milk ejection were also not found to be significantly different between breastfeeding and pumping. CONCLUSION: This study suggests that milk ejection patterns remain consistent within individual mothers regardless of whether the mother is breastfeeding or expressing milk indicating a likelihood of the process either being programmed or innate to the individual.

Early initiation and regular breast milk expression reduces risk of lactogenesis II delay in at-risk Singaporean mothers in a randomised trial.

INTRODUCTION: Lactogenesis II (LaII) failure can be prevented in at-risk mothers with simple proactive interventions. In a randomised trial, we investigated the efficacy of early and regular breast milk expression in establishing LaII, using an electric double-breast pump. METHODS: Mothers with uncomplicated singleton deliveries were randomised to intervention (n = 31) or control (n = 29) groups. The former commenced breast milk expression with an electric pump within one hour of delivery and maintained regular expression with direct breastfeeding. Control mothers directly breastfed without regular pump expression. Expressed milk volumes were analysed for citrate, lactose, sodium and protein. RESULTS: Median time of LaII was Day 3 (interquartile range [IQR] 1 day) with intervention and on Day 4 (IQR 1 day) among controls (p = 0.03). Biochemical steady-state concentrations were achieved around early Day 4 (sodium, total protein) and Days 4-5 (citrate, lactose). Sodium, protein and lactose levels were similar in both groups over seven days, at 5.80 mM, 0.68 mM and -13.38 mM, respectively. Mean daily milk volume with intervention was 73.9 mL on Day 3 and 225.2 mL on Day 7, greater than controls (25.4 mL on Day 3 and 69.2 mL on Day 7; p < 0.2). Mean infant weights were similar on Day 8 at 3,477 g with intervention and 3,479 g among controls. CONCLUSION: LaII is established by postnatal Day 3 with early initiation of regular breast milk expression, a useful intervention for mothers at risk of early-onset breastfeeding failure.

The bioactive nature of human breastmilk.

Human breastmilk is widely accepted to be the optimal source for nutrition for the newborn infant, containing all the proteins, lipids, carbohydrates, micronutrients and trace elements required for growth, development and immune protection. In addition human breastmilk plays a significant role in the prevention of medical conditions such as childhood cancers, obesity and gastrointestinal diseases. The importance of breastmilk and its superiority as a source of infant nutrition is highlighted in the recent overhaul of teh World Health Organization growth charts that are now based on exclusively breastfed infants. Human breastmilk also contains a population of cells, the importance of which is often not considered when the bioactivity of breastmilk is discussed.

Unravelling the mystery of stem/progenitor cells in human breast milk.

BACKGROUND: Mammary stem cells have been extensively studied as a system to delineate the pathogenesis and treatment of breast cancer. However, research on mammary stem cells requires tissue biopsies which limit the quantity of samples available. We have previously identified putative mammary stem cells in human breast milk, and here, we further characterised the cellular component of human breast milk. METHODOLOGY/PRINCIPAL FINDINGS: We identified markers associated with haemopoietic, mesenchymal and neuro-epithelial lineages in the cellular component of human breast milk. We found 2.6 ± 0.8% (mean ± SEM) and 0.7 ± 0.2% of the whole cell population (WCP) were found to be CD133+ and CD34+ respectively, 27.8 ± 9.1% of the WCP to be positive for Stro-1 through flow-cytometry. Expressions of neuro-ectodermal stem cell markers such as nestin and cytokeratin 5 were found through reverse-transcription polymerase chain reaction (RT-PCR), and in 4.17 ± 0.2% and 0.9 ± 0.2% of the WCP on flow-cytometry. We also established the presence of a side-population (SP) (1.8 ± 0.4% of WCP) as well as CD133+ cells (1.7 ± 0.5% of the WCP). Characterisation of the sorted SP and non-SP, CD133+ and CD133- cells carried out showed enrichment of CD326 (EPCAM) in the SP cells (50.6 ± 8.6 vs 18.1 ± 6.0, P-value  = 0.02). However, culture in a wide range of in vitro conditions revealed the atypical behaviour of stem/progenitor cells in human breast milk; in that if they are present, they do not respond to established culture protocols of stem/progenitor cells. CONCLUSIONS/SIGNIFICANCE: The identification of primitive cell types within human breast milk may provide a non-invasive source of relevant mammary cells for a wide-range of applications; even the possibility of banking one's own stem cell for every breastfeeding woman.

Importance of vacuum for breastmilk expression.

OBJECTIVE: To determine the effect of the strength of applied vacuum on the flow rate and yield of breastmilk using an electric breast pump. STUDY DESIGN: Twenty-one breastfeeding mothers and two expressing mothers expressed their breastmilk for 15 minutes using an electric breast pump set at their own maximum comfortable vacuum, and at one to three softer vacuums. Milk yield and flow rate were measured. RESULTS: At the maximum comfortable vacuum (-190.7 +/- 8.8 mm Hg) 4.3 +/- 0.4 milk ejections occurred during 15 minutes of expression and yielded 118.5 +/- 11.4 mL of milk (65.5 +/- 4.1% of the available milk). Softer vacuums yielded less milk volume (p < 0.05) and less of the available milk (p < 0.01). Milk flow rate was greater during the first milk ejection than the third or subsequent milk ejections (p < 0.001). Cream content of the milk was highest after expressing for 15 minutes using the mother's maximum comfortable vacuum. CONCLUSIONS: Use of the mother's maximum comfortable vacuum enhances milk flow rate and milk yield. The cream content of the milk at the end of the expression period was an indicator of how effectively the breast had been drained.

Identification of nestin-positive putative mammary stem cells in human breastmilk.

Stem cells in mammary tissue have been well characterised by using the mammary stem cell marker, cytokeratin (CK) 5 and the mature epithelial markers CK14, CK18 and CK19. As these markers have never been reported in cells from breastmilk, the aim of this study has been to determine whether mammary stem cells are present in expressed human breastmilk. Cultured cells from human breastmilk were studied by using immunofluorescent labelling and reverse transcription/polymerase chain reaction (RT-PCR). We found a heterogeneous population of cells with differential expression of CK5, CK14, CK18 and CK19. Further, by using the multipotent stem cell marker, nestin, we identified cells in culture that were positive only for nestin or double-positive for CK5/nestin, whereas no co-staining was observed for CK14, CK18 and CK19 with nestin. When cells isolated from breastmilk were analysed by using RT-PCR prior to culture, only nestin and CK18 were detected, thereby indicating that breastmilk contained differentiated epithelial and putative stem cells. Furthermore, fluorescence-activated cell-sorting analysis demonstrated, in breastmilk, a small side-population of cells that excluded Hoechst 33342 (a key property of multipotent stem cells). When stained for nestin, the cells in the side-population were positive, whereas those not in the side-population were negative. The presence of nestin-positive putative mammary stem cells suggests that human breastmilk is a readily available and non-invasive source of putative mammary stem cells that may be useful for research into both mammary gland biology and more general stem cell biology.

Milk flow rates can be used to identify and investigate milk ejection in women expressing breast milk using an electric breast pump.

Currently there is no simple method available to assess milk ejection and breast milk flow in lactating women in both the clinical and research setting. The authors hypothesize that changes in milk flow rate are associated with milk ejection and therefore may provide a method suitable for the assessment of milk ejection and removal. Mothers (n = 23) expressed milk from one breast for a 15-minute period using both weak and strong vacuums on two to four separate occasions using an experimental electric breast pump (Medela AG, Baar, Switzerland). Breast milk flow rates were recorded at 5-second intervals by connecting a tube from the breast shield to a bottle placed on a balance that was connected to a computer. Milk ejection was determined by an acute increase in milk duct diameter in the contralateral breast using ultrasound (Acuson XP10, Siemens, Mountain View, CA), and the change in duct diameter was compared with milk flow rates. Milk flow rates ranged from 0 to 4.6 g per 5-second period. Increases in flow rates were positively associated with increases in duct diameter (p < 0.05). Furthermore, within each milk ejection, higher maximum duct diameters were positively related to greater volumes expressed per 5-second periods (p < 0.001). Time to the first milk ejection and number of milk ejections were the same when determined by ultrasound or flow rates. This direct relationship between increases in duct diameter and acute increases in milk flow rates suggests that changes in flow rates can be used to identify milk ejection in the absence of ultrasound data.

Volume and frequency of breastfeedings and fat content of breast milk throughout the day.

OBJECTIVE: We aimed to provide information that can be used as a guide to clinicians when advising breastfeeding mothers on normal lactation with regard to the frequency and volume of breastfeedings and the fat content of breast milk. METHODS: Mothers (71) of infants who were 1 to 6 months of age and exclusively breastfeeding on demand test-weighed their infants before and after every breastfeeding from each breast for 24 to 26 hours and collected small milk samples from each breast each time the infant was weighed. RESULTS: Infants breastfed 11 +/- 3 times in 24 hours (range: 6-18), and a breastfeeding was 76.0 +/- 12.6 g (range: 0-240 g), which was 67.3 +/- 7.8% (range: 0-100%) of the volume of milk that was available in the breast at the beginning of the breastfeeding. Left and right breasts rarely produced the same volume of milk. The volume of milk consumed by the infant at each breastfeeding depended on whether the breast that was being suckled was the more or less productive breast, whether the breastfeeding was unpaired, or whether it was the first or second breast of paired breastfeedings; the time of day; and whether the infant breastfed during the night or not. Night breastfeedings were common and made an important contribution to the total milk intake. The fat content of the milk was 41.1 +/- 7.8 g/L (range: 22.3-61.6 g/L) and was independent of breastfeeding frequency. There was no relationship between the number of breastfeedings per day and the 24-hour milk production of the mothers. CONCLUSIONS: Breastfed infants should be encouraged to feed on demand, day and night, rather than conform to an average that may not be appropriate for the mother-infant dyad.

Milk prolactin, feed volume and duration between feeds in women breastfeeding their full-term infants over a 24 h period.

Previous studies have suggested that the uptake of prolactin from the blood into the milk may be restricted when the alveolus is distended with milk. Therefore the aim of this study was to determine the relationship between prolactin in milk and milk production by measuring the concentration of prolactin in samples of fore- and hind-milk as well as the volume of milk removed for each breast, at each breastfeed over a 24 h period. The mean (+/- S.D.) concentration of prolactin in milk for all women (n = 15) over the 24 h period was 18.5 +/- 11.6 microg l(-1) (fore-milk) and 16.8 +/- 12.8 microg l(-1) (hind-milk). The variation between women masked small changes within women in the concentration of prolactin in milk over the 24 h period, therefore a prolactin ratio (individual fore- or hind-milk value divided by the mean for all fore- or hind-milk samples collected over a 24 h period) was determined. The concentration of prolactin was highest in milk between 02.01 and 06.00 h (prolactin ratio for fore- to hind-milk, 1.5), and lowest between 10.01 and 18.00 h (prolactin ratio for fore- to hind-milk, 0.8). Furthermore, we observed that the difference in prolactin concentration between the fore- and hind-milk (fore-hind gradient) was greatest between 06.01 and 10.00 h (4 microg l(-1)). To ensure that this effect was not due to permeability in the paracellular pathway, the concentrations of serum albumin and sodium in milk were measured. No significant (P > 0.05) changes over the 24 h period, or with increasing time since last feed were observed. We therefore concluded that when the breast is most drained of milk (in the late evening), and the rate of milk synthesis is greatest, the fore-hind prolactin gradient in the milk of the following feed (in the early morning) is highest. This is consistent with the observation that prolactin uptake from the blood by the lactocyte is dependent on the fullness of the breast, such that prolactin uptake may be inhibited in full alveoli.

Initiation of lactation in women after preterm delivery.

BACKGROUND: Lactogenesis II describes the onset of copious milk secretion, and the success of lactogenesis II has been determined in women by measuring the changes in the composition of mammary secretion in the immediate postpartum period. AIM AND METHODS: Therefore, the aim of this study was to determine the success of lactogenesis II at day 5 postpartum in women expressing milk for their preterm infants (n = 22) by measuring the lactogenesis II markers (milk citrate, lactose, sodium and total protein) and comparing them with women breastfeeding full-term infants (n = 16). RESULTS: There were no significant differences between the means (+/- SD) of the lactogenesis II markers for preterm (4.3 +/- 0.7 mM; 147 +/- 10 mM; 12 +/- 6 mM; 14.0 +/- 1.5 g/l, respectively) and term (3.4 +/- 1.4 mM; 126 +/- 17 mM; 30 +/- 13 mM; 15.3 +/- 2.5 g/l, respectively) women. However, variation about the mean was greater in preterm women (coefficient of variation for citrate, 40%; lactose, 14%; sodium, 42%; and total protein, 17%) compared with term women (17%, 7%, 33%, and 10%, respectively). All lactogenesis II markers were within 3 SD from the means for the term women and thus these women were considered to have successfully initiated their lactation. Only 18% of preterm women had all four lactogenesis II markers within 3 SD from the mean for term women. The remaining 82% of preterm women had at least one of the markers of lactogenesis II at pre-initiation concentrations (36% had 1 marker, 32% had 2 markers, and 14% had 3 markers). Furthermore, these women had significantly lower 24-hr milk production than those preterm women that had all four markers within 3 SD from the mean of the term women. CONCLUSIONS: It was concluded that 82% of preterm women had a compromised initiation of lactation, and this was not uniform in all women.