Comparison of Inductively Coupled Plasma Optical Emission Spectrometry with an Ion Selective Electrode to Determine Sodium and Potassium Levels in Human Milk

Biomarker-based text messages to promote lactation success in mothers of critically Ill infants: a randomized controlled pilot study

OBJECTIVE

Infrequent breast pumping limits mother's own milk production in mothers of infants admitted to the neonatal intensive care unit. We aimed to determine the feasibility and benefit of biomarker-based personalized text messages on pumping frequency and milk sodium levels. A secondary aim examined lactation outcomes.

STUDY DESIGN

In this randomized controlled pilot study, 51 mothers were randomized to receive personalized text messages regarding pumping frequency or standard care.

RESULTS

There were no differences in pumped milk volume or sodium level, however, there was a trend towards the intervention group pumping more frequently, which was significant on day 5 (p = 0.035), and they lactated nearly 9 days longer. Post-hoc analysis found the intervention group tended to be more likely to pump ≥ 500 mL by day14 (p = 0.08), a marker of long-term lactation success.

CONCLUSION

Personalized biomarker-based text messages are feasible and may support lactation in mothers of critically ill infants.

Early postpartum pumping behaviors, pumped milk volume, and achievement of secretory activation in breast pump-dependent mothers of preterm infants

OBJECTIVE

Pumping studies in mothers of preterm infants are limited by self-reported pumping behaviors and non-objective measures of pumped milk volume and secretory activation (SA).

METHODS

Non-randomized observational study of first 14 days postpartum in 29 mothers of preterm infants. Smart pumps measured and stored pumping behaviors and pumped milk volume. Selective ion electrodes measured sodium and sodium:potassium ratio to determine SA. Generalized estimating equations, cluster analyses and multivariate regression were used.

RESULTS

SA was delayed (median 5.8 days) and impermanent. Each additional daily pumping increased odds of SA within 2 days by 48% (p = 0.01). High-intensity pumping mothers (N = 17) had greater daily and cumulative pumped milk volume than low-intensity pumping mothers (N = 12). Pumping variables showed daily changes in the first week, then plateaued.

CONCLUSION

The first week postpartum is critical for optimizing pumping behaviors. Accurate, objective measures of pumping behaviors, pumped milk volume and SA are a research priority.

Association between maternal stress and premature milk cortisol, milk IgA, and infant health: a cohort study

Background

Maternal stress is pervasive in the neonatal intensive care unit (NICU). Maternal stress is associated with changes in human milk (HM) immunomodulatory agents, which may impact neonatal health. We sought to determine the association between maternal stress, HM immunoglobulin A (IgA) and cortisol, and to assess how these milk components correlate with infant immune and neurodevelopmental outcomes. We then compared how these associations persist over time.

Methods

The study design involved a cohort study of exclusively breastfeeding mothers and their singleton moderately preterm (28-34 weeks) infants admitted to the NICU. We collected maternal serum, maternal saliva, and first-morning whole milk samples, and administered maternal stress questionnaires at 1 and 5 weeks postpartum. We analyzed the samples for HM IgA (using a customized immunoassay in skim milk) and for HM and salivary cortisol (using a chemiluminescent immunoassay). Infant illness was assessed using the Score for Neonatal Acute Physiology II (SNAP II) and SNAP II with Perinatal Extension (SNAPPE II), and infant neurodevelopment were assessed using the Test of Infant Motor Performance. We analyzed changes in HM IgA and cortisol over time using paired t-tests. Furthermore, we performed correlation and regression analyses after adjusting for gestational age (GA), corrected GA, and infant days of life.

Results

In our study, we enrolled 26 dyads, with a mean maternal age of 28.1 years, consisting of 69% white, 19% Black, and 8% Hispanic. Cortisol: Salivary and HM cortisol were closely associated in week 1 but not in week 5. Though mean salivary cortisol remained stable over time [2.41 ng/mL (SD 2.43) to 2.32 (SD 1.77), p = 0.17], mean HM cortisol increased [1.96 ng/mL (SD 1.93) to 5.93 ng/mL (SD 3.83), p < 0.001]. Stress measures were inversely associated with HM cortisol at week 1 but not at week 5. IgA: HM IgA decreased over time (mean = -0.14 mg/mL, SD 0.53, p < 0.0001). High maternal stress, as measured by the Parental Stressor Scale: neonatal intensive care unit (PSS:NICU), was positively associated with HM IgA at week 5 (r = 0.79, P ≤ 0.001). Higher IgA was associated with a lower (better) SNAP II score at week 1 (r = -0.74, p = 0.05). No associations were found between maternal stress, salivary cortisol, HM cortisol, or HM IgA and neurodevelopment at discharge (as assessed using the TIMP score). Furthermore, these relationships did not differ by infant sex.

Conclusion

Maternal stress showed associations with HM cortisol and HM IgA. In turn, HM IgA was associated with lower measures of infant illness.

Mammary epithelium permeability during established lactation: associations with cytokine levels in human milk

Objective

The cytokine profile of human milk may be a key indicator of mammary gland health and has been linked to infant nutrition, growth, and immune system development. The current study examines the extent to which mammary epithelium permeability (MEP) is associated with cytokine profiles during established lactation within a sample of US mothers.

Methods

Participants were drawn from a previous study of human milk cytokines. The present analysis includes 162 participants (98 Black, 64 White) with infants ranging from 1 to 18 months of age. Levels of cytokines were determined previously. Here we measure milk sodium (Na) and potassium (K) levels with ion-selective probes. Two approaches were used to define elevated MEP: Na levels ≥10 mmol/L and Na/K ratios greater than 0.6. Associations between maternal-infant characteristics, elevated MEP, and twelve analytes (IL-6, IL-8, TNFα, IL-1β, FASL, VEGFD, FLT1, bFGF, PLGF, EGF, leptin, adiponectin) were examined using bivariate associations, principal components analysis, and multivariable logistic regression models.

Results

Elevated MEP was observed in 12 and 15% of milk samples as defined by Na and Na/K cutoffs, respectively. The odds of experiencing elevated MEP (defined by Na ≥ 10 mmol/L) were higher among Black participants and declined with older infant age. All cytokines, except leptin, were positively correlated with either Na or the Na/K ratio. A pro-inflammatory factor (IL-6, IL-8, TNFα, IL-1β, EGF) and a tissue remodeling factor (FASL, VEGFD, FLT1, bFGF, PLGF, adiponectin) each contributed uniquely to raising the odds of elevated MEP as defined by either Na or the Na/K ratio.

Conclusion

This exploratory analysis of MEP and cytokine levels during established lactation indicates that elevated MEP may be more common in US populations than previously appreciated and that individuals identifying as Black may have increased odds of experiencing elevated MEP based on current definitions. Research aimed at understanding the role of MEP in mammary gland health or infant growth and development should be prioritized.

Milk Biomarkers of Secretory Activation in Breast Pump-Dependent Mothers of Preterm Infants: An Integrative Review

Background: Lack of mother's own milk (MOM) at discharge from the neonatal intensive care unit (NICU) is a global problem and is often attributable to inadequate MOM volume. Evidence suggests that the origins of this problem are during the first 14 days postpartum, a time period that includes secretory activation (SA; lactogenesis II, milk coming in). Objectives: To describe and summarize evidence regarding use of MOM biomarkers (MBMs) as a measure of SA in pump-dependent mothers of preterm infants in the NICU and to identify knowledge gaps requiring further investigation. Methods: An integrative review was conducted using Whittemore and Knafl methodology incorporating the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) checklist. A search using electronic databases MEDLINE (through PubMed) and CINAHL (Cumulative Index to Nursing and Allied Health Literature) and reference lists of included articles was conducted. Results: Of the 40 articles retrieved, 6 met the criteria for inclusion. Results revealed the following five findings: (1) Achievement of SA defined by MBMs is delayed and/or impaired in mothers of preterm infants. (2) MBMs are associated with pumped MOM volume. (3) Achievement of SA defined by MBMs is associated with pumping frequency. (4) Delayed and/or impaired achievement of SA defined by MBMs may be exacerbated by maternal comorbidities. (5) There is a lack of consensus as to which MBM(s) and analysis techniques should be used in research and practice. Conclusions: MBMs hold tremendous potential to document and monitor achievement of SA in mothers of preterm infants, with multiple implications for research and clinical practice.

Novel At-Home Mother's Milk Conductivity Sensing Technology as an Identification System of Delay in Milk Secretory Activation Progress and Early Breastfeeding Problems: Feasibility Assessment

BACKGROUND

Prolonged exclusive breastfeeding is a public health priority and a personal desire by mothers; however, rates are low with milk supply challenges as a predominant cause. Early breastfeeding management at home is key. Milk electrolytes, mainly sodium ions, are accepted as biomarkers of secretory activation processes throughout the first weeks after birth and predictors for prolonged breastfeeding success, although they are not incorporated into routine care practice.

OBJECTIVE

The aim of this study was to test the feasibility of a novel handheld smartphone-operated milk conductivity sensing system that was designed to compute a novel parameter, milk maturation percent (MM%), calculated from milk sample conductivity for tracking individual secretory activation progress in a real-world home setting.

METHODS

System performance was initially evaluated in data collected from laboratory-based milk analysis, followed by a retrospective analysis of observational real-world data gathered with the system, on the spot in an at-home setting, implemented by lactation support providers or directly by mothers (N=592). Data collected included milk sample sensing data, baby age, and self-reported breastfeeding status and breastfeeding-related conditions. The data were retroactively classified in a day after birth-dependent manner. Results were compared between groups classified according to breastfeeding exclusivity and breastfeeding problems associated with ineffective breastfeeding and low milk supply.

RESULTS

Laboratory analysis in a set of breast milk samples demonstrated a strong correlation between the system's results and sodium ion levels. In the real-world data set, a total of 1511 milk sensing records were obtained on the spot with over 592 real-world mothers. Data gathered with the system revealed a typical time-dependent increase in the milk maturation parameter (MM%), characterized by an initial steep increase, followed by a moderate increase, and reaching a plateau during the first weeks postpartum. Additionally, MM% levels captured by the system were found to be sensitive to breastfeeding status classifications of exclusive breastfeeding and breastfeeding problems, manifested by differences in group means in the several-day range after birth, predominantly during the first weeks postpartum. Differences could also be demonstrated for the per-case time after birth-dependent progress in individual mothers.

CONCLUSIONS

This feasibility study demonstrates that the use of smart milk conductivity sensing technology can provide a robust, objective measure of individual breastfeeding efficiency, facilitating remote data collection within a home setting. This system holds considerable potential to augment both self-monitoring and remote breastfeeding management capabilities, as well as to refine clinical classifications. To further validate the clinical relevance and potential of this home milk monitoring tool, future controlled clinical studies are necessary, which will provide insights into its impact on user and care provider satisfaction and its potential to meet breastfeeding success goals.

The Utilization of Sodium Concentration in Human Milk from Pump-Dependent Mothers of Preterm Infants as a Measure of Milk Production

Objective: This study investigated changes in sodium concentrations in human milk from mothers of premature infants using different breast pumps for 14 days postpartum, and the correlation between the sodium concentration in mother's own milk (MOM) and the volume pumped. Study Design: This randomized controlled study recruited 66 mothers of premature infants delivered in our hospital from February to December 2018, and we assigned them to three groups using an envelope method. In intervention group 1, a hospital-grade electric breast pump was used from postpartum day 1 to 14; in intervention group 2, a hospital-grade electric breast pump was used on postpartum days 1 to 5 and a normal personal electric breast pump on postpartum days 6 to 14; in the control group, a personal normal electric breast pump was used from postpartum day 1 to 14. Data recorded included the breast milk volume pumped and milk sodium concentration. Results: The average daily volume of MOM pumped differed statistically (p < 0.05) between the intervention and control groups at postpartum days 7 and 14. The average daily volume pumped did not differ between intervention groups 1 and 2 by postpartum day 14 (p > 0.05). However, the time taken for the sodium concentrations to normalize differed significantly (p < 0.01). At postpartum day 5, the sodium concentrations of 73% of intervention group 1 and 2 mothers were within normal limits, and they were maintained until day 14. In comparison, only 41% of the controls had normal MOM sodium levels on day 5, and they were still high on day 7 in 27.3% of controls. Conclusions: In the early stage of lactation initiation (within 5 days postpartum), using a hospital-grade electric breast pump promotes lactation in mothers who deliver prematurely and the sodium concentrations normalize more quickly. Sodium can be used as an objective biomarker of MOM to evaluate the possibility of delayed lactation in mothers of premature infants, and it could assist interventions in the early postpartum period. Trial Registration: Chinese Clinical Trial Registry, ChiCTR2200061384.

Leveraging mHealth and a milk expression frequency biomarker during postpartum to prolong lactation among parents of critically ill infants: a pilot study

OBJECTIVE

To assess the feasibility and potential benefits of personalized biomarker-based text messages in prolonging lactation among parents of critically ill infants.

STUDY DESIGN

Thirty-six participants were randomized to receive either daily texts with Mother's Own Milk (MOM) sodium levels or standard care. Surveys at months 1 and 3 assessed whether infants were receiving exclusive MOM feeding, any MOM feeding, and whether the parent was still lactating. Kaplan-Meier and log-rank tests were used for time-to-event analysis within and between intervention and control groups.

RESULTS

Participants were predominantly on Medicaid (72%), delivered infants <1500 g, and by c-section (56%). Kaplan-Meier probabilities at month 3 suggest prolonged MOM feeding (63% [0.95CI, 0.43-0.91] vs. 41% [0.95CI, 0.21-0.67]) and lactation (63% [0.95CI, 0.42-0.95] vs. 37% [0.95CI, 0.18-0.76]) in the enhanced group compared to the control group.

CONCLUSION

Personalized biomarker-based text messages are feasible and may prolong lactation and MOM feeding among parents of critically ill infants.

Pharmacokinetic and Bioequivalent Study of Potassium Chloride Sustained-Release Tablet Under Different Dietary Conditions in Healthy Chinese Subjects

Potassium (K⁺ ) is an endogenous substance that is an essential dietary component. However, the interaction between dietary arrangements and specific effects of dietary K⁺ intake in bioequivalence studies remains unclear. To investigate the influence of dietary arrangement on the bioequivalence of potassium chloride (KCl) sustained-release tablets in healthy Chinese volunteers, the pharmacokinetics of KCl were compared in two open-label, single-center, randomized, two-period crossover studies with different dietary conditions. All volunteers received an oral dose of 6 g of KCl sustained-release tablets under fasting conditions, with different dietary arrangements. Urine samples were collected on baseline days and 48 hours after tablet consumption. Inductively coupled plasma-optical emission spectrometry was used to measure the concentration of K⁺ in the urine samples. Pharmacokinetic parameters were analyzed using Phoenix WinNonlin software in a noncompartmental model. In either clinical trial, no significant differences were observed in the maximal rate of urinary excretion and cumulative urinary excretion from 0 to 24 hours of K⁺ between the reference and test drugs. The bioequivalence studies of both KCl sustained-release tablet formulations were successfully conducted under different dietary conditions.

Associations of Secretory Activation Breast Milk Biomarkers with Breastfeeding Outcome Measures

OBJECTIVE

The objective of this study was to explore associations between day 10 postpartum (D10) secretory activation biomarkers and the breastfeeding outcome measures.

STUDY DESIGN

This prospective longitudinal descriptive study collected antepartum, D10, and day 60 postpartum (D60) questionnaire data and D10 milk samples. Protein, lactose, and citrate were analyzed with enzymatic spectrophotometric assays. Sodium and potassium were analyzed with inductively coupled plasma optical emission spectrophotometry. Group comparison data were analyzed using χ², Fisher exact, and independent sample t tests, as appropriate, using SPSS for Mac (version 28).

RESULTS

Participants (n = 92) provided a D10 breastmilk sample and completed D10 questionnaires, and 83 completed D60 questionnaires. Participants with D10 impaired secretory activation sodium (>23.0 mM) were more likely to report D10 perceived insufficient milk supply, χ² = 7.002, P < .05; and less D10 feeding/pumping frequency a day, P < .05; and partial breastfeeding at D60, P < .05. Additionally, participants with D10 impaired secretory activation sodium-to-potassium ratio (sodium: potassium) > 0.8 were more likely to partially breastfeed at D60, P < .05.

CONCLUSION

Elevated milk sodium and sodium: potassium are biomarkers related to variables indicative of low milk supply. Therefore, immediate milk testing can be useful in identifying lactation compromise and improving breastfeeding duration. Because breastfeeding affords maternal and infant health benefits, clinicians should identify ways to measure lactation compromise in conjunction with an examination and clinical history to provide early interventions to increase breastfeeding duration and exclusivity.

Human Milk Sodium and Potassium as Markers of Mastitis in Mothers of Preterm Infants

Introduction: This prospective longitudinal study examined changes in milk sodium concentration (Na) and sodium:potassium ratio (Na:K), microbiological culture, milk production, and breast health in relation to mastitis after preterm birth. Methods: We studied women who gave birth at 29-34 weeks of gestation in a tertiary obstetric hospital in Perth, Western Australia. Milk samples, 24-hour milk production, and breast health data were collected every second day to day 10 postpartum, then every third day until infant discharge from the neonatal unit. Milk Na and K were measured at point of care (POC) using handheld ion selective meters, and Na:K calculated. Cultures were performed on postnatal days 8, 13, and every 6 days thereafter. For episodes of mastitis, milk was cultured at onset, and Na and Na:K measured daily until resolution. Women were followed up at 4 and 8 weeks postpartum. Results: In a sample of 44 women, 4 mastitis cases were detected in 3 women during their infants' neonatal stay; all had elevated milk Na and Na:K that resolved within 48 hours; 2/4 experienced reduced milk production and 1/4 had heavy growth of Staphylococcus epidermidis. A further 2 mastitis cases were reported in 39 women followed up to 8 weeks postpartum. Four women had elevated milk Na and Na:K without clinical signs of mastitis; three also had reduced milk production. Conclusions: POC testing of milk Na and/or Na:K may offer a useful indicator of breast health. Mastitis may cause an acute reduction in milk production regardless of the presence of culture-positive infection.

Reliability of an Ion-Selective Electrode as a Simple Diagnostic Tool for Mastitis

BACKGROUND

Developing a simple quantitative tool for mastitis diagnosis is essential. The Ion-Selective Electrode for sodium has been reported to reliably measure sodium concentrations in human milk.

RESEARCH AIM

To determine whether an Ion-Selective Electrode measurement of sodium:potassium ratios could serve as a diagnostic tool for mastitis and, if so, to determine the diagnostic cut-off value.

METHODS

A total of 107 milk samples, including 55 from milk bank donors and 52 from participants with mastitis, were studied. The sodium:potassium ratios were determined in 33 samples (without mastitis n = 15; with mastitis n = 18) by the Ion-Selective Electrode and ion chromatography. The remaining 74 samples (donor milk n = 40; participants with mastitis n = 34) were analyzed by Ion-Selective Electrode only. Values were averaged over three measurements for each method.

RESULTS

The median postpartum months of donors and participants with mastitis were 2 and 3 months, respectively. The mean (SD) sodium:potassium ratios without and with mastitis were 0.5 (0.1) and 1.7 (1.2), respectively. A positive correlation existed between sodium:potassium ratios obtained from the two methods (r = 0.98). Area under the curve values were 0.951 (95% CI [0.904, 0.986]) for the Ion-Selective Electrode (N = 107) and 0.978 (95% CI [0.926, 1.000]) for the ion chromatography (n = 33) methods. The optimal cut-off value for the Ion-Selective Electrode method was 0.60, with 86.5% sensitivity and 92.7% specificity.

CONCLUSIONS

The Ion-Selective Electrode was sufficiently accurate for the diagnosis of mastitis. Cohort studies are needed to explore the relationship between sodium:potassium ratios and clinical outcomes.

Prepregnancy Body Mass Index Is Associated with Time-Dependent Changes in Secretory Activation Measures During the First 7 Days Postpartum in Breast Pump-dependent Mothers of Premature Infants

Background: Little is known about the biology of secretory activation (SA) in overweight and obese (OW/OB) mothers who are breast pump dependent with a premature infant in the neonatal intensive care unit. Objective: To compare time-dependent changes in daily pumped milk volume, maternal milk sodium (Na) concentration, and Na-to-potassium (K) ratios (Na:K) in the first 14 days postpartum in breast pump-dependent mothers with prepregnancy body mass index (BMI) <27 and BMI ≥27 kg/m². Design/Methods: This secondary analysis for 39 subjects, 44% (n = 17) with prepregnancy BMI <27 and 56% (n = 22) with BMI ≥27, included transformed data of outcome measures, chi-square, t-tests, and growth curve models. Results: For days 1-7, daily pumped milk volume increased significantly more rapidly for mothers with BMI <27 (65.82 mL/d) versus BMI ≥27 (33.08 mL/d), but the daily rate of change in pumped milk volume during days 8-14 was not statistically different. Daily milk Na concentration decreased significantly faster in BMI <27 (-3.93 mM/d) versus BMI ≥27 (-2.00 mM/day) during days 1-7, but was not significantly different for days 8-14. No statistical differences were noted for Na:K ratio for either time period. Conclusion: These data add biologic evidence to previous research, suggesting delayed or impaired SA in OW/OB mothers, and suggest that the window of opportunity for research and clinical interventions is days 1-7 postpartum in this population.

Use of a Portable Point-of-Care Instrumentation to Measure Human Milk Sodium and Potassium Concentrations

Objective: Human milk (HM) sodium (Na) and potassium (K) concentrations, as well as the Na and K ratio (Na:K), are associated with stages of lactation and breast health. Portable point-of-care instruments to measure HM biomarkers related to secretory activation or tight junction disturbances would supply clinicians immediate information for individualized lactation care. This study compared HM concentrations of Na and K and Na:K measured by a biochemist with inductively coupled plasma optical emission spectrometry (ICP-OES) and measured by a clinician with ion-selective electrode probes (ISEPs). Design: HM samples (n = 92) were participant collected and donated on day 10 postpartum through a convenience sample of breastfeeding women in West Michigan. Na and K concentrations were determined using ICP-OES and ISEPs. Bland-Altman plots, paired sample t-test, and logistic regressions were completed using R 3.4.4 and R Studio 1.2.1335 with package Lattice. Results: Na concentrations were not significantly different with ICP-OES (13.0 ± 14.8 mM) and ISEPs (12.6 ± 13.7 mM, p = 0.06), whereas K concentrations (ICP-OES 16.1 ± 1.9 mM, ISEPs 14.4 ± 2.4 mM, p < 0.001) and Na:K (ICP-OES 0.81 ± 0.92, ISEPs 1.01 ± 1.62, p = 0.011) were significantly different. Between both methods, the Na, K, and Na: K linear relationships were statistically significant. Conclusion: With additional longitudinal and clinical usefulness research clinicians could use ISEPs to collect and interpret relevant lactation data to support individualized lactation interventions.

The association of maternal gestational hyperglycemia with breastfeeding duration and markers of milk production

BACKGROUND

Previous studies focusing on the association between gestational diabetes and breastfeeding duration have been inconclusive.

OBJECTIVES

We aimed to determine whether maternal gestational hyperglycemia is associated with the duration of breastfeeding and the concentrations of markers linked to breastmilk production.

METHODS

Data from the prospective, multiethnic Growing Up in Singapore Towards Healthy Outcomes study were used to assess the association of fasting plasma glucose (FPG) and 2-h postglucose challenge (2hPG) measured at 26-28 wk of gestation with duration of breastfeeding and concentrations of protein, lactose, citrate, sodium, potassium, and zinc in breastmilk 3 wk postpartum.

RESULTS

Of the 1035 participants, 5.2% and 9.5% had elevated FPG and 2hPG, respectively, consistent with a diagnosis of gestational diabetes mellitus based on International Association of Diabetes and Pregnancy Study Groups criteria. FPG ≥5.1 mmol/L was associated with a crude reduction in median breastfeeding duration of 2.3 mo. In a model adjusted for maternal prepregnancy BMI and intention to breastfeed, FPG ≥5.1 mmol/L predicted earlier termination of any breastfeeding (adjusted HR: 1.47; 95% CI: 1.04, 2.08) but not full breastfeeding (adjusted HR: 1.08; 0.76, 1.55). 2hPG ≥8.5 mmol/L was not significantly associated with the durations of any (adjusted HR: 0.86; 95% CI: 0.62, 1.19) or full (adjusted HR: 0.85; 95% CI: 0.62, 1.18) breastfeeding. Maternal FPG was significantly and positively associated with breastmilk sodium (adjusted coefficient: 1.28; 95% CI: 1.08, 1.51) and sodium-to-potassium ratio (adjusted coefficient: 1.29; 95% CI: 1.08, 1.54) but not with other measured breastmilk components.

CONCLUSIONS

Women with FPG ≥5.1 mmol/L during pregnancy breastfeed for a shorter duration. Future work involving measurement of milk production is needed to determine whether low milk production predicts breastfeeding duration among women with elevated FPG. This trial was registered at www.clinicaltrials.gov as NCT01174875.

25 Years of Research in Human Lactation: From Discovery to Translation

Researchers have recently called for human lactation research to be conceptualized as a biological framework where maternal and infant factors impacting human milk, in terms of composition, volume and energy content are studied along with relationships to infant growth, development and health. This approach allows for the development of evidence-based interventions that are more likely to support breastfeeding and lactation in pursuit of global breastfeeding goals. Here we summarize the seminal findings of our research programme using a biological systems approach traversing breast anatomy, milk secretion, physiology of milk removal with respect to breastfeeding and expression, milk composition and infant intake, and infant gastric emptying, culminating in the exploration of relationships with infant growth, development of body composition, and health. This approach has allowed the translation of the findings with respect to education, and clinical practice. It also sets a foundation for improved study design for future investigations in human lactation.

Indicators of Secretory Activation in Mothers of Preterm Very Low Birth Weight Infants

BACKGROUND

Inconsistent information exists regarding indicators of secretory activation in mothers delivering very low birth weight infants.

RESEARCH AIMS

To compare time to the onset of secretory activation using three separate indicators. A secondary aim examined the association between indicators of secretory activation and milk production.

METHODS

Indicators of secretory activation included maternal perception, volume attainment (production of ≥ 20 mL in two consecutive expression sessions) and biomarkers (sodium and lactose) obtained at volume attainment. Milk production was measured on Days 1-7 and then weekly for 6 weeks.

RESULTS

In 69 mothers of infants born ≤ 32 weeks' gestation and < 1500 g, we found no correlation in time to secretory activation between indicators. Earlier volume attainment was associated with increased milk production on Days 1-7, 14, 21, and 28 (all p < .007). Participants who exhibited both normal lactose and sodium levels produced more milk on Days 28 and 42 (p = .028 and .011), those with only normal lactose levels produced more on Day 42 (p = .026) and those with only normal sodium levels on Day 28 (p = .036). Earlier secretory activation by volume attainment was associated with increased expression frequency during Days 2-5 (all p < .014) and participants with normal biomarkers expressed more frequently during Days 2-5 (all p < .020).

CONCLUSION

Mothers of very low birth weight infants are at risk for delayed secretory activation, which may decrease their milk production. Frequent expression during the first 5 days postpartum may promote earlier secretory activation. Valid methods of determining secretory activation are necessary to develop interventions promoting earlier secretory activation.

Mother's Own Milk Biomarkers Predict Coming to Volume in Pump-Dependent Mothers of Preterm Infants

OBJECTIVE

To assess serial secretory activation biomarker concentrations (sodium [Na], potassium [K], Na:K, protein, lactose, and citrate) in mother's own milk (MOM) from breast pump-dependent mothers of preterm infants to determine associations with coming to volume (CTV), defined as producing at least 500 mL/day MOM by day 14 postpartum.

STUDY DESIGN

We collected serial MOM samples and pumped MOM volume data for 14 days postpartum in mothers who delivered at <33 weeks of gestation. Regression models and the Mann-Whitney U test were used to evaluate associations.

RESULTS

Among 40 mothers, 39 (mean gestational age, 28.8 weeks; 67% overweight/obese; 59% nonwhite) had paired MOM volume and biomarker data; 33% achieved CTV between postpartum days 6 and 14. In univariate models, MOM Na on postpartum day 5 and Na:K on days 3 and 5 were associated with CTV. Mothers achieving CTV were more likely to have postpartum Na:K ≤1 on day 3 (75% vs 25%; P = .06) and ≤0.8 on day 5 (69% vs 10%; P < .01). In a multivariable regression model, day 5 Na:K (1 unit decrease in Na:K: OR, 18.7; 95% CI, 1.13-311.41; P = .049) and maternal prepregnancy body mass index (BMI) (1 unit increase in BMI: OR, 0.88; 95% CI, 0.78-0.99; P = .04) were associated with CTV between postpartum days 6 and 14.

CONCLUSIONS

Secretory activation and CTV were compromised in breast pump-dependent mothers with preterm delivery. CTV was predicted by MOM Na level and Na:K. These biomarkers have potential as objective point-of-care measures to detect potentially modifiable lactation problems in a high-risk population.

Quantification of Process Lethality (5-Log Reduction) of Salmonella and Salt Concentration during Sodium Replacement in Biltong Marinade

Salt (sodium chloride, NaCl) is commonly used in ready-to-eat (RTE) meat products such as biltong, a South African style dried beef product for flavor, enhanced moisture loss, and reduction of microbial growth. However, increased consumption of high sodium content foods is commonly associated with high blood pressure and heart disease. This study evaluated the use of alternative salts, potassium chloride (KCl) and calcium chloride (CaCl₂) in the biltong marinade to achieve a ≥ 5-log reduction of Salmonella, a pathogen of concern in beef products. Beef pieces (1.9 cm × 5.1 cm × 7.6 cm) were inoculated with a five-serovar mixture of Salmonella (Salmonella Thompson 120, Salmonella Enteritidis H3527, Salmonella Typhimurium H3380, Salmonella Heidelberg F5038BG1, and Salmonella Hadar MF60404), vacuum-tumbled in a traditional biltong marinade of salt, spices, and vinegar containing either NaCl, KCl or CaCl₂ (2.2% concentration) followed by an 8-10 day drying period at 23.9 °C (75 °F) and 55% relative humidity. Microbial enumeration of Salmonella was conducted following inoculation, after marination, and after 2, 4, 6, 8, and 10 days of drying in a humidity/temperature chamber. Biltong produced with CaCl₂, NaCl, or KCl achieved a > 5-log reduction of Salmonella after 6, 7, and 8 days, respectively. The Salmonella reduction trends with biltong made with NaCl or CaCl₂ were not significantly different (p < 0.05) while both were significantly different from that made with KCl (p > 0.05). Sodium, calcium, and potassium ion concentrations were measured using ion-specific electrode meters following biltong processing and drying. As expected, the biltong made with the corresponding salt had the most abundant ion in the sample. Regardless of the salt used in the marinade, the potassium ion levels were moderately elevated in all samples. This was determined to be from potassium levels naturally present in beef rather than from other ingredients. Sampling of several commercial brands of biltong for sodium content showed that some were significantly above the allowable level of claims made on package ingredient statements. The substitution of NaCl with KCl or CaCl₂ during biltong processing can also provide a 5-log reduction of Salmonella to produce a safe product that can be marketed as a more healthy low-sodium food alternative that may appeal to consumers who need to reduce their blood pressure and are conscientious of sodium levels in their diet.

Evidence-Based Updates on the First Week of Exclusive Breastfeeding Among Infants ≥35 Weeks

The nutritional and immunologic properties of human milk, along with clear evidence of dose-dependent optimal health outcomes for both mothers and infants, provide a compelling rationale to support exclusive breastfeeding. US women increasingly intend to breastfeed exclusively for 6 months. Because establishing lactation can be challenging, exclusivity is often compromised in hopes of preventing feeding-related neonatal complications, potentially affecting the continuation and duration of breastfeeding. Risk factors for impaired lactogenesis are identifiable and common. Clinicians must be able to recognize normative patterns of exclusive breastfeeding in the first week while proactively identifying potential challenges. In this review, we provide new evidence from the past 10 years on the following topics relevant to exclusive breastfeeding: milk production and transfer, neonatal weight and output assessment, management of glucose and bilirubin, immune development and the microbiome, supplementation, and health system factors. We focus on the early days of exclusive breastfeeding in healthy newborns ≥35 weeks' gestation managed in the routine postpartum unit. With this evidence-based clinical review, we provide detailed guidance in identifying medical indications for early supplementation and can inform best practices for both birthing facilities and providers.

Measures of Secretory Activation for Research and Practice: An Integrative Review

Background: Maternal concern about inadequate milk volume commonly emerges in the first 2 weeks postpartum, a critical lactation period that includes secretory activation. This review summarizes the biology of secretory activation and evaluates the accuracy and feasibility of published measures of secretory activation. Materials and Methods: A systematic search of measures of secretory activation for mothers of healthy term and preterm infants yielded 62 abstracts. Following additional screening, 15 publications qualified for quantitative synthesis review and were evaluated with respect to accuracy (validated with another measure of secretory activation in the same mother) and feasibility (accessibility, cost, and ease of use). Results:Maternal perception of milk coming in (MP) is the most feasible measure, but its accuracy has not been established. Patterns of increase in maternal milk volume have been validated with maternal milk-borne biomarkers in breastfeeding, and breast pump-dependent mothers and normal values have been published. Accuracy of serial maternal urinary lactose concentrations has not been established for secretory activation and lacks feasibility. Maternal milk biomarkers are the accurate standard to which other measures are compared but currently lack feasibility for routine use. Conclusions: Use of secretory activation measures can personalize lactation care by matching maternal risk with appropriate diagnostics. Priorities for research and practice include validation of MP as a population-based screening tool, implementation of techniques that measure patterns of increase in milk volume for moderate risk populations, and the development of milk biomarker science for point-of-care use in the most complicated lactation scenarios.