Breast Pumps and Mastitis in Breastfeeding Women: Clarifying the Relationship.

Mastitis is a debilitating condition that can impact around 20% of mothers and is characterized by fever, flu-like symptoms and tender, swollen areas of the breasts. Despite the emerging evidence that breast milk dysbiosis is an underlying cause of mastitis, breast pumps have been implicated as a predisposing risk factor in the pathophysiology of mastitis in breastfeeding mothers. Previous studies have suggested that the use of a breast pump increases a mother's risk for developing mastitis, however, incidence rates of mastitis over the stages of lactation do not match breast pump usage rates. Furthermore, breast pumps, even when used at low vacuum, still promote some breast drainage, thus avoiding milk stasis, which is considered a key factor in the development of mastitis. As a consequence, these data suggest that the literature association of breast pumps with mastitis is more a case of reverse causation and not direct association. Moreover, it is important to note that breast pumps are actually a part of the conservative management of mastitis. In combination, these data show that the breast pump should not be considered a driver in the pathophysiology of mastitis in women.

Breast shield design impacts milk removal dynamics during pumping: A randomized controlled non-inferiority trial.

INTRODUCTION: While many studies have investigated the importance of optimizing pumping patterns for milk removal, the influence of breast shield design on milk removal has not been the focus of extensive investigation. This study aimed to determine the effectiveness of breast shields with either a 105° or a 90° flange opening angle on breast drainage and milk volume expressed during pumping. MATERIAL AND METHODS: This study was a cross-over, randomized controlled non-inferiority trial (Registration; NCT03091985). Mothers (n = 49) of breastfeeding infants participated in the study over two study sessions. Participants were randomly assigned to pump both breasts simultaneously for 15 minutes with either the 105° or 90° breast shield in the first session, and the other shield in the second session. Effectiveness (breast drainage) and efficiency (volume expressed) of both breast shields were assessed after 15 minutes of pumping. Intention-to-treat and per protocol analyses were performed to determine if the 105° breast shield was non-inferior to the 90° breast shield for breast drainage and volume expressed. Perceived comfort was assessed via questionnaire. RESULTS: The 105° breast shield was both non-inferior and superior compared to the standard 90° shield for breast drainage (intention-to-treat, 3.87% (0.01-7.72), P = .049) and volume expressed (intention-to-treat, 9.14 mL (1.37-16.91), P=.02). In addition, the 105° shield was rated as feeling more comfortable (P < .001) and as having an improved fit to the breast (P < .001) compared to the 90° shield. CONCLUSIONS: Expressing with the 105° breast shield was more efficient, effective and comfortable compared to the 90° shield. Breast shield design can significantly impact pumping outcomes, and an opening angle of 105° improves both the dynamics and comfort of milk removal.

Short-term rate of milk synthesis and expression interval of preterm mothers.

AIM: To determine the impact of the pumping regimes of women with preterm infants on the daily milk production, and on the short-term rate of milk synthesis during early lactation to support evidence-based recommendations for optimising milk production. METHODS: Mothers of preterm infants (n=25) recorded start time, finish time and expression volumes from every breast expression on days 10, 15-20 postpartum. RESULTS: Expressing more often than five times per day did not result in a significant increase in daily milk production. Milk volume per expression per breast increased for intervals between expressions of between 2and6 hours then reached a plateau when the interval between expression was 7 hours or longer. The short-term rate of milk synthesis decreased as the interval between expressions increased until about 7.5 hours at which point it begun to increase (p value associated with interval between expressions^2<0.001). CONCLUSION: The strong inverse association between the short-term rate of milk synthesis and the interval between expressions for intervals up to 7 hours suggest that the maximum interval between expressions should be 7 hours. Data suggest that, on average, the mothers should express at least five times a day to maximise daily milk production. Considering inter-individual variation, determination of an individual mother's maximum interval between expressions that does not compromise the short-term rate of milk synthesis will help to optimise daily milk production while minimising the demands on the mother's time.

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.

Longitudinal changes in breastfeeding patterns from 1 to 6 months of lactation.

OBJECTIVE: The most common reason given for discontinuation of exclusive breastfeeding is perceived insufficient milk supply. Breastfed infants show more variation in feeding frequency than bottle-fed infants, and this may lead to a mother lacking confidence in her milk supply if the frequency of breastfeeding sessions does not match expectations based on bottle feeding. We aimed to assist clinicians in supporting breastfeeding mothers by providing evidence-based information on expected changes in breastfeeding patterns and milk intake during exclusive breastfeeding for 6 months. SUBJECTS AND METHODS: Mothers and their healthy infants who were exclusively breastfeeding (total 24-hour milk intake within the normal range) were studied during two to five 24-hour periods between 1 and 6 months of lactation. RESULTS: Between 1 and 3 months of lactation, the frequency of breastfeeding sessions decreased, whereas both the median and maximum breastmilk intakes during each breastfeeding session increased. These parameters remained constant between 3 and 6 months. The duration of each breastfeeding session decreased steadily from 1 to 6 months, but the total 24-hour milk intake remained constant. CONCLUSIONS: Breastfeeding becomes more efficient between 1 and 3 months of lactation, although milk intake remains constant. Clinicians can give mothers confidence that these changes in breastfeeding behavior do not indicate insufficient milk supply, but may be a result of the increase in the stomach capacity of the infants and are an expected outcome of a healthy, normal breastfeeding relationship.

Why calcium in breastmilk is independent of maternal dietary calcium and vitamin D.

Adequate calcium intake is vital for infant health, and some cases of rickets have been associated with a low concentration of calcium in breastmilk. The concentration of calcium in breastmilk has been shown to vary widely both between mothers, and over the course of lactation. To address potential concerns about the adequacy of calcium intake for infants who are exclusively breastfed, we discuss the factors likely to be affecting the concentration of calcium in breastmilk. We review and provide new evidence for a physicochemical model of the interactions of calcium with other components of breastmilk, particularly phosphate, citrate and casein. A proposed mechanism for the control of the concentration of calcium in milk is described that highlights the influence of the concentrations of citrate and casein. Understanding these interactions clarifies why the concentration of calcium in breastmilk is not affected by manipulations of maternal dietary calcium and vitamin D.

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.

Tongue movement and intra-oral vacuum in breastfeeding infants.

OBJECTIVE: The mechanism by which the breastfeeding infant removes milk from the breast is still controversial. It is unclear whether the infant uses predominantly intra-oral vacuum or a peristaltic action of the tongue to remove milk from the breast. The aim of this study was to use ultrasound to observe movements of the tongue during breastfeeding and relate these movements to both milk flow and simultaneous measurements of intra-oral vacuum. METHODS: Submental ultrasound scans of the oral cavity of 20 breastfed infants (3-24 weeks old) were performed during a breastfeed. Intra-oral vacuums were measured simultaneously via a milk-filled supply line (SNS) connected to a pressure transducer. RESULTS: Vacuum increased during the downward motion of the posterior tongue and at the same time milk flow and milk ducts in the nipple was observed. Peak vacuum (-145+/-58 mmHg) occurred when the tongue was in the lowest position. CONCLUSIONS: Ultrasound imaging demonstrated that milk flow from the nipple into the infant's oral cavity coincided with both the lowering of the infants tongue and peak vacuum. Therefore vacuum is likely to play a major role in milk removal from the breast.

The effects of fish oil supplementation in pregnancy on breast milk fatty acid composition over the course of lactation: a randomized controlled trial.

This study evaluated the longitudinal effect of fish oil in pregnancy on breast milk fatty acid composition and infant outcomes. In a randomized, controlled trial, 98 women received 2.2 g docosahexaenoic acid (DHA) and 1.1 g eicosapentaenoic acid (EPA) or olive oil from 20 wk of gestation until delivery. Fatty acid composition in breast milk (at 3 d, 6 wk, and 6 mo) and infant erythrocyte membranes (at 1 y) were determined by gas liquid chromatography. Breast milk fatty acids were examined in relationship to growth and development. Compared with control group, breast milk from women who received fish oil had proportionally higher DHA and EPA levels at 3 d and 6 wk after delivery, but this difference was no longer apparent by 6 mo. Infant DHA status at 1 y of age was directly related to DHA levels at 3 d, 6 wk, and 6 mo postpartum (but not to antenatal supplementation). Both EPA and DHA in breast milk were positively correlated with Griffith's developmental scores including hand and eye coordination. Thus, supplementation in pregnancy was associated with increased n-3 long-chain polyunsaturated fatty acids (LCPUFAs) in breast milk, particularly in early lactation, and this was positively associated with infant DHA status at 1 y.

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.

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.

Excretion of lactose in urine as a measure of increased permeability of the lactating breast during inflammation.

HYPOTHESIS: The increased excretion of lactose in urine will be an accurate predictor of increased breast permeability during inflammation of the breast and therefore could predict whether there is a relationship between the severity and type of symptoms suffered during mastitis and changes in breast permeability. METHODS: Twenty-six mothers were followed prospectively from Day 5 postpartum to the end of their lactation. Milk from each breast, blood, 24-hour urine samples, and data on breast and systemic pathologies were collected at reference intervals during the first three months postpartum, daily during the occurrence of any breast inflammation and 7 days after resolution of symptoms. RESULTS: The 24-h excretion of lactose in urine was higher during mastitis (p < 0.001), peaking at the commencement of the mastitis and decreasing over time until there was no significant difference at the time of follow-up when compared to mothers without mastitis (p < 0.25). The changes in lactose in urine were consistent with the changes in sodium, chloride, and lactose in milk, confirming milk expressed for sample analysis was representative of milk from the site of inflammation. Increased severity of breast symptoms experienced during mastitis was a significant predictor for an increased excretion of lactose in urine (p < 0.022). CONCLUSIONS: The use of 24-h excretion of lactose in urine provided a reliable marker of changes occurring in breast permeability and subsequently has shown that an increasing area of inflammation of the breast was predictive of an increase in breast permeability and associated changes in milk composition.

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.

The use of ultrasound to characterize milk ejection in women using an electric breast pump.

This study aimed to use ultrasound imaging to investigate the milk ejection characteristics of women during a 10-minute expression using an electric breast pump capable of applying 2 markedly different vacuum patterns. The classic pattern (47 cycles/min) and 3-phase pattern (pre-milk ejection: 120 cycles/min, post-milk ejection: 20 cycles/min for 2 minutes post-milk ejection then 55-78 cycles/min for 8 minutes) were tested, and the milk expressed was collected in 30-second intervals. Multiple milk ejections (96%) were detected (classic: 3.27+/-2.05; 3-phase: 3.72+/-1.19) and associated with increases in milk flow. Almost half of the total volume of milk expressed was removed during the first milk ejection (classic: 41.38+/-21.48%; 3-phase: 46.72+/-26.60%). There was no correlation between the number of milk ejections and both the total volume of milk and percentage of available milk for either pattern. In conclusion, milk ejection characteristics and efficiency of milk expression did not change in response to different expression patterns.

Infant intake of fatty acids from human milk over the first year of lactation.

Despite the importance of human milk fatty acids for infant growth and development, there are few reports describing infant intakes of individual fatty acids. We have measured volume, fat content and fatty acid composition of milk from each breast at each feed over a 24 h period to determine the mean daily amounts of each fatty acid delivered to the infant from breast milk at 1, 2, 4, 6, 9 and 12 months of lactation in five women. Daily (24 h) milk production was 336.60 (SEM 26.21) and 414.49 (SEM 28.39) ml and milk fat content was 36.06 (SEM 1.37) and 34.97 (SEM 1.50) g/l for left and right breasts respectively over the course of the first year of lactation. Fatty acid composition varied over the course of the day (mean CV 14.3 (SD 7.7) %), but did not follow a circadian rhythm. The proportions (g/100 g total fatty acids) of fatty acids differed significantly between mothers (P<0.05) and over the first year of lactation (P<0.05). However, amounts (g) of most fatty acids delivered to the infant over 24 h did not differ during the first year of lactation and only the amounts of 18:3n-3, 22:5n-3 and 22:6n-3 delivered differed between mothers (P<0.05). Mean amounts of 18:2n-6, 18:3n-3, 20:4n-6 and 22:6n-3 delivered to the infant per 24 h over the first year of lactation were 2.380 (SD 0.980), 0.194 (SD 0.074), 0.093 (SD 0.031) and 0.049 (SD 0.021) g respectively. These results suggest that variation in proportions of fatty acids may not translate to variation in the amount delivered and that milk production and fat content need to be considered.

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.

Efficacy of breast milk expression using an electric breast pump.

The authors compared breastfeeding and expression characteristics in 30 mothers of exclusively breastfeeding, healthy term infants. Mean (+/- SD) volume per breastfeed from one breast was 71.8 +/- 26.3 mL, and mean duration per breastfeed for one breast was 16.6 +/- 10.5 minutes. Mean volume of milk expressed in 5 minutes from one breast was 60.6 +/- 39.0 mL and corresponded to the expression of 99.4 +/- 82.6% of the milk stored in the breast. The rate of milk expression differed greatly between mothers (P = .0001) but remained constant for the first 2.5 minutes before decreasing with time (P = .0001). These results show the mean breastfeed volume was similar to the volume of milk expressed in a 5-minute period. Furthermore, this study is the first to establish protocols that allow for the objective determination of breast pump efficacy.

Effect of vacuum profile on breast milk expression using an electric breast pump.

The authors compared milk expression using 5 experimental vacuum patterns and a commercially available vacuum pattern ranging in cycle times (20 to 78 cycles/min) and vacuum curve dynamics in 30 mothers using an experimental, software-controlled electric breast pump. The volume of milk removed over 5 minutes differed (P = .0072) between patterns (range = 62.8 +/- 6.6 mL to 47.2 +/- 5.1 mL). However, there was no difference in the percentage of available milk removed (range = 99.4% +/- 15.1% to 70.6% +/- 8.6%). The rate of milk removal differed between patterns at both the beginning (1 minute) and end (1.5 minutes) of the expression period (P < .05). Peak vacuum chosen differed between patterns (P = .0085) but was not related to either the volume or percentage of available milk expressed. Breastfeeding characteristics did not differ between poor and successful expressers. These results show that breast milk expression by an electric breast pump can be influenced by the vacuum pattern.

Variation in fat, lactose and protein in human milk over 24 h and throughout the first year of lactation.

Fat in human milk is extremely variable and can represent up to 50 % of infant energy intake. To accurately determine milk composition and infant intake at 1 (n 17), 2 (n 17), 4 (n 17), 6 (n 15), 9 (n 6) and 12 (n 5) months of lactation, samples of fore- and hind-milk were collected from each breast at each feed over 24 h periods from an initial group of seventeen women. The content of fat in milk varied over 24 h, with a mean CV of 47.6 (se 2.1) % (n 76) and 46.7 (se 1.7) % (n 76) for left and right breasts respectively. The 24 h amounts of fat, lactose and protein in milk differed between women (P=0.0001), but were consistent between left and right breasts. Daily milk production differed between breasts (P=0.0001) and women (P=0.0001). Accordingly, amounts of fat (P=0.0008), lactose (P=0.0385) and protein (P=0.0173) delivered to the infant over 24 h also differed between breasts and women (P=0.0001). The energy content of milk and the amount of energy delivered to the infant over 24 h were the same between breasts, but differed between women (P=0.0001). The growth rate of a group of only six infants in the present study was not related to either the concentrations or amounts of fat, lactose, protein and energy in milk over the first 6 months of life. These results show the individuality of milk composition and suggest that only a rigorous sampling routine that takes into account all levels of variation will allow the accurate determination of infant intake of fat, lactose, protein and energy.