Journal of Human Lactation

Evidence on the beneficial effects of microorganisms in human milk is emerging. Obesity and gestational diabetes mellitus appear to be related to alterations in the maternal gut microbiota and human milk composition. However, knowledge about the influence of maternal obesity and gestational diabetes mellitus on the human milk microbiota remains limited.

To summarize and systematically assess the evidence on the influence of obesity and gestational diabetes mellitus on the diversity and/or composition of the human milk microbiota.

A systematic review following PRISMA guidelines was conducted. Searches were performed in the MEDLINE, Cochrane Database of Systematic Reviews, Web of Science, and EMBASE, as well as in ClinicalTrials.gov and the World Health Organization International Clinical Trials Registry Platform. The ROBINS-E tool was used to assess the risk of bias. Out of 1,473 studies identified and 24 protocol records, eight studies were selected for final analysis.

Exposure to gestational diabetes mellitus and maternal obesity were associated with changes in the human milk microbiota's diversity and/or composition. Lactating women exposed to obesity had a higher prevalence of Staphylococcus and a lower prevalence of Bifidobacterium in their milk. Those exposed to gestational diabetes mellitus had a higher prevalence of Staphylococcus, Gemella, and Prevotella. Findings regarding bacterial phyla prevalence were inconclusive.

Based on the findings presented in this systematic review, it is not yet possible to draw definitive conclusions regarding the true influence of maternal obesity and/or gestational diabetes mellitus on the diversity or composition of the human milk microbiota.

Human milk contains messenger ribonucleic acid (mRNA), a key player in protein production and a source of gene expression information for understanding lactation physiology. The mRNA is renowned for its fragility and exists in several milk fractions, creating practical challenges for mRNA isolation and analysis. While research teams have developed protocols for the use of human milk samples in transcriptomic applications, it is unclear whether there are best practices in sample collection, storage, and processing procedures for the collection of the highest quality mRNA.

We aim to review current practices in the collection, storage, and processing of human milk relevant for its use in transcriptomic applications (using mRNA) in the last 10 years.

The PubMed database was systematically searched for publications addressing methodological considerations or the use of mRNA derived from human milk samples.

Most sources described the collection of human milk from small cohorts of term mothers in a mature lactational stage. While fresh collection of human milk was common, some was frozen or preserved. Several centrifugation protocols exist, and considerations for collection, storage, and processing may vary by transcriptomic application. There is inconsistency in the description and reporting of mRNA quality used in analyses that obfuscates the determination of best practices for best mRNA quality.

Research into the effects of human milk collection, processing, and storage on mRNA quality metrics is warranted.

Perinatal loss is a time of intense grief for affected parents. Due to lactation physiology, bereaved mothers still experience the onset of lactation and are left with milk but no child to feed.

To explore what is known about the lactation experiences of (1) mothers and (2) support providers, including healthcare workers, milk banks, and families, during periods of perinatal bereavement.

A scoping review, guided by Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines, was undertaken using two database searches to identify existing research (n = 24 studies). The research team extracted data from studies and categorized results into four categories that were developed after reading full texts: (1) Producing Milk, (2) Support, (3) Stopping Lactation, and (4) Donating Milk. Due to the large amount of qualitative data, additional qualitative analysis was conducted to identify six prominent themes: (1) Hurting, (2) Lacking, (3) Valuing, (4) Succeeding, (5) Connecting, and (6) Redeeming.

Most of the included studies focused on mothers, and a limited number focused on support providers. Additionally, most studies were qualitative (19 of 24). Producing milk during bereavement was a way of connecting, while lactation support and stopping lactation were often characterized as lacking. Finally, donating milk was frequently perceived as redeeming. Across all categories, there were limited quantitative outcomes.

Bereaved lactation has predominantly been studied through qualitative research methods, with some common themes emerging. Quantitative research is needed to better understand the types and prevalence of lactation support provided during perinatal bereavement, as well as the donation patterns, barriers, and enablers of bereaved milk bank donors.

Dysphoric Milk Ejection Reflex (D-MER) is defined as an undesirable feeling that some breastfeeding women experience within seconds of milk letdown. D-MER can impact maternal psychological well-being and breastfeeding continuation, but it is an understudied phenomenon.

To uncover and understand D-MER among breastfeeding women within 3 years of birth who self-identified as having experienced D-MER.

This descriptive qualitative research study was conducted to uncover and understand breastfeeding experiences of women who self-identify as experiencing D-MER. We conducted in-depth interviews with 13 women about their D-MER experience(s). Interview data were qualitatively analyzed using Braun and Clarke’s thematic analysis for descriptive studies.

We found four themes that captured participants’ perceptions, emotional reactions, and behavioral responses to D-MER: (A) Breastfeeding concessions and toleration; (B) Something does not feel “normal”; (C) I remember a feeling like this before; and (D) This is real, and recognition is validating. Themes reflected an outsized influence of D-MER on participants’ breastfeeding goals, trajectories, and maternal identities. Participants expressed frustration about the lack of recognition and help for D-MER among healthcare providers, but relief in understanding, often through social media, that D-MER was considered a real, physiological condition. Participants were able to reduce, but not eliminate, D-MER symptoms through trial-and-error processes, including distraction, operant conditioning, and mindfulness/relaxation.

D-MER had a profound, negative impact on participants’ breastfeeding experiences and led to decisions to stop breastfeeding or consider stopping before a participant had originally intended. Research is needed to develop interventions that reduce or eliminate D-MER symptomology.

Sexual and gender minority adults are increasingly growing their families and having children, yet there is limited information on the lactation experiences of sexual and gender minority parents.

Using data from The PRIDE Study, a national cohort of sexual and gender minority adults in the United States, we examined patterns and correlates of lifetime breast/chestfeeding among sexual minority (i.e., lesbian, bisexual, queer) cisgender women, transgender women, transgender men, and gender diverse individuals who were parents.

Our analysis included 1,562 parents aged 19–83 years with a median of two children (IQR 1–3). Among this population, 941 (60.2%) were sexual minority cisgender women, 232 (14.9%) transgender women, 199 (12.7%) transgender men, and 190 (12.2%) gender diverse parents assigned female at birth. Among 962 parents who had ever carried a pregnancy and delivered a child, sexual minority cisgender women were most likely to have ever breast/chestfed (91.7%), followed by gender diverse parents (88.8%) and transgender men (83.3%). No other demographic factors were associated with ever breast/chestfeeding. Few participants (6.7%) had ever breast/chestfed a child from another person’s pregnancy. Ever having delivered a child and having an increasing number of children were associated with ever breast/chestfeeding a child from another person’s pregnancy. In addition, seven (3%) transgender women had ever breast/chestfed a child.

In our cohort, rates of lifetime breast/chestfeeding were high among sexual and gender minority parents who had ever carried a pregnancy. Breast/chestfeeding provides important health and infant–parent bonding benefits in families where one or more parents has the interest in and capacity for lactation. Co-lactation and/or lactation induction may be particularly beneficial for sexual and gender minority families.

Research and education on lactation often overlooks the needs and experiences of transgender men and non-binary individuals who are chestfeeding. Support from partners and compassionate, informed healthcare practitioners can significantly enhance their chestfeeding experience.

Guided by queer phenomenology, the purpose of this study was to explore the experiences of chestfeeding from the perspectives of transgender men and non-binary people.

This qualitative study followed the tenets of interpretive description. Semi-structured interviews were conducted with transgender men and non-binary people in Ontario, Canada, who had recent chestfeeding experiences.

Transgender men and non-binary people (N = 8) identified a variety of facilitators and barriers to chestfeeding. Having access to support systems, knowledgeable practitioners who provide gender-affirming care, and bodily autonomy were protective factors through the chestfeeding experience. In addition, planning and preparing for chestfeeding experiences added to positive experiences with chestfeeding. Gender dysphoria and transphobic societal norms were barriers to chestfeeding.

The chestfeeding experiences of transgender men and non-binary parents are shaped by the presence or absence of gender-affirming and knowledgeable care. Disorienting experiences, including misgendering and inadequate support, can disrupt lactation and harm well-being, while affirming interactions enhance embodiment and self-advocacy. This study suggests there is a need for inclusive policies, comprehensive provider education, and practices that affirm diverse gender identities across the perinatal period.

Breastfeeding continuation can be challenging for patients undergoing surgical procedures. Guidelines regarding peri-surgical measures and medication use are available, but it is not clear to what extent these are applied in clinical practice and how the care is experienced by breastfeeding mothers.

To describe patient perspectives on perioperative support for breastfeeding mothers undergoing surgical procedures.

An online, cross-sectional study was conducted among adult Belgian women who received analgesics or anesthetics during a surgical procedure while breastfeeding. The pre-tested survey assessed beliefs about breastfeeding and its health benefits, perioperative practices used and experienced, medication use, and advice related to breastfeeding and human milk.

From September 2021 through April 2022, 193 participants completed the questionnaire. In all, 45 participants (23.3%) reported that no healthcare provider asked about their breastfeeding status prior to their procedure, and 43 (22.3%) reported no discussion on medication use and safety during breastfeeding. Guidance on breastfeeding management varied widely, with conflicting advice: 47 (24.4%) were advised to breastfeed immediately after the procedure, while 84 (43.5%) ultimately did. In contrast, 11 (5.7%) were advised to express and discard their milk once, 37 (19.2%) for 12 hours, and 31 (16.1%) for 24 hours after the procedure, while 10 (5.2%), 28 (14.5%), and 21 (10.9%) ultimately did, respectively. Many sought information beyond their healthcare team, for example, in online forums (n = 77; 39.9%) and websites (n = 50; 25.9%).

While awareness of breastfeeding benefits is generally good amongst breastfeeding mothers, women’s experiences around breastfeeding support during surgical procedures vary, often not reflecting the most recent evidence-based standards. Better education of healthcare professionals, more comprehensive surgical protocols, or greater awareness of existing guidelines could help to meet the need for breastfeeding support during surgery.

Evidence-based maternity practices advanced by the Baby-Friendly Hospital Initiative (BFHI) are associated with increased human milk feeding and improved maternal and infant health. However, inequitable distribution of BFHI facilities contributes to disparities in access to evidence-based practices. ENRICH Carolinas (ENRICH) provided technical assistance to birthing facilities across North and South Carolina to improve maternity practices by advancing toward BFHI or state-level designation.

To compare changes in maternity practices for participating and non-participating facilities during the period of the technical assistance initiative using Maternity Practices in Infant Nutrition and Care (mPINC) data.

We obtained data from the United States Centers for Disease Control and Prevention (CDC) 2018, 2020, and 2022 mPINC surveys of birthing facilities in North and South Carolina (N = 98). The CDC calculates a total mPINC score for each facility to indicate its overall support for optimal infant feeding and subscores for immediate postpartum care, rooming-in, feeding practices, feeding education and support, discharge support, and institutional management. Scores range from 0 to 100, with higher scores indicating better practices. We conducted a longitudinal analysis using linear mixed-effects modeling to assess the association between participation in the ENRICH technical assistance initiative and changes in scores over time.

Findings show that facilities which participated in the technical assistance initiative had significantly larger increases in total mPINC scores from 2018 to 2022, with an average unadjusted total score 4.8 points higher (95% CI [0.6, 9.2, p = 0.03]) than non-participating facilities, despite scores not being significantly different at baseline. ENRICH facilities made particular progress in rooming-in and institutional management compared with non-ENRICH facilities.

Facilities participating in a two state systems-level technical assistance initiative provide more optimal care and support for infant feeding practices than non-participating facilities, suggesting this initiative may improve access to evidence-based maternity care.

Low milk supply is a common problem in lactation, yet it is difficult to study and manage due to multifactorial causes and inconsistent measurement across research and clinical practice.

To synthesize current subjective and objective approaches to assessing low milk supply, including scales and survey items, infant weight trajectories and test-weight procedures, milk expression protocols, biomarkers, and device-based metrics. For each method, we appraise validity, feasibility, and potential harms.

In both research and clinical settings, low milk supply is measured inconsistently and imprecisely. Tools available to assess maternal perception of low milk supply and quantify infant milk intake and production all have limitations.

Combining self-report and objective measurements and selecting measurement tools specific to the outcome of interest can help with accurate identification and management of low milk supply.

Human milk sub-sampling protocols are used in lactation research to estimate milk composition, while minimizing interference with normal breastfeeding. However, macronutrient concentrations in human milk can be highly variable, and the accuracy of sub-sampling protocols for a single breastfeed is currently unknown.

We investigated the accuracy of three milk sub-sampling protocols for estimating the macronutrient concentrations of a complete feed: the mean of pre- and post-feed samples, pre-feed samples only, and post-feed samples only.

In this observational study, macronutrient concentrations from each sub-sampling protocol were compared to the volume-weighted average of the complete pumping session, based on foremilk, bulk milk, and hindmilk samples from 15 mothers. Macronutrient concentrations of each milk fraction were measured with a human milk analyzer. Additionally, correlations between macronutrient concentrations and lactation characteristics were studied.

Macronutrient concentrations from each sub-sampling protocol were strongly correlated with the volume-weighted average reference concentrations. Significant biases were found for the fat concentration (between -1.3 and +1.9 g/dl, depending on the protocol), but not for protein and carbohydrate concentrations.

For the fat concentration, none of the three sub-sampling protocols was accurate. The mean of pre- and post-feed samples could, however, be used for high-fat milk samples where measurement errors exceed the bias (+0.3 g/dl). Pre-feed or post-feed samples only should not be used to estimate the fat concentration of a complete feed. For proteins and carbohydrates, one milk sample taken at any moment in a breastfeed is sufficient to represent the concentration in the complete feed.

Major pregnancy complications, such as hypertensive disorders of pregnancy, gestational diabetes mellitus, delivery of a small for gestational age infant, preterm delivery, and placental abruption, are associated with the development of Type II diabetes mellitus and cardiovascular disease. Improving breastfeeding longevity may reduce long-term risk for cardiovascular disease for those with major pregnancy complications. Metabolic syndrome (i.e., the presence of at least three specific cardiovascular disease risk factors) is an appropriate marker to assess future cardiovascular risk in the early postpartum.

To determine whether lactation intensity in the first 6 months postpartum is associated with metabolic syndrome at 6 months postpartum among people who previously had a major pregnancy complication.

This is a prospective observational cohort study is being conducted at a tertiary hospital in Adelaide, South Australia (ANZCTN12624001351505). We will be recruiting a total of 250 participants referred to a postpartum cardiovascular clinic after experiencing a major complication in pregnancy. To assess lactation intensity, participants complete online questionnaires on infant feeding patterns for 6 months postpartum. We will examine the relationship between lactation intensity and the development of metabolic syndrome at 6 months postpartum via binary logistic regression.

Results of this study aid our understanding of the complex relationship between major pregnancy complications, early postpartum metabolic syndrome, and lactation. This data will inform whether interventions to support lactation should be leveraged to prevent primary cardiovascular disease in these high-risk pregnancy cohorts.

While prior studies have established associations between specific factors and delayed onset of Lactogenesis II, critical gaps remain in understanding how the timing of lactogenesis initiation dynamically affects macronutrient levels within 72 hours postpartum, and whether modifiable factors alter these relationships.

To validate known risk factors for delayed lactogenesis in a Chinese population; characterize time-specific macronutrient changes; and evaluate how modifiable factors (e.g., gestational diabetes mellitus) influence human milk composition.

In this prospective cohort study, 360 participants were interviewed during the first 24 hours postpartum in China. At 24-hour intervals, the onset of lactogenesis was determined based on maternal perception. The participants were divided into delayed onset of lactogenesis and onset of lactogenesis groups. Human milk samples were collected at 24, 48, and 72 hours postpartum, and their macronutrient content (lactose, fat, and protein) was determined using a human milk analyzer.

Approximately 23.6% (n = 85) of participants experienced delayed lactogenesis, which was significantly associated with gestational diabetes mellitus, Cesarean delivery, and pre-pregnancy body mass index ≥ 25.0 kg/m² (odds ratio [95% confidence interval] = 2.32 [1.20, 4.50], 2.02 [1.20, 3.41], and 2.75 [1.23, 6.18], respectively).

Lactose concentration was significantly lower in the delayed onset of lactogenesis group at 24 hours: Wald χ²(1) = 23.71, p < 0.001, and 48 hours: Wald χ²(1) = 8.26, p = 0.04, as well as in those with gestational diabetes at 24 hours postpartum: Wald χ²(1) = 9.60, p = 0.002.

Beyond confirming known risk factors for delayed lactogenesis in China, our identification of time-dependent lactose deficiency highlights the need for lactose concentration monitoring within the first 48 hours postpartum.

According to the human milk banking guidelines in Japan, issued in 2014, pasteurized donor human milk (PDHM) is discarded 24 hours after thawing. However, previous studies have suggested that PDHM remains safe for administration to preterm infants for up to 48 hours after thawing, potentially reducing unnecessary wastage.

This study aimed to assess the microbiological safety and the preservation of nutritional and immunological properties of PDHM stored under refrigeration for up to 48 hours after thawing.

This was a paired-sample experimental study evaluating the safety and composition of PDHM during refrigerated storage after thawing. Individual pasteurized milk samples from 40 donors were thawed overnight in a refrigerator and analyzed at 24 and 48 hours. Samples were cultured on sheep blood agar and incubated for 48 hours at 35 °C to assess bacterial growth. Macronutrients, micronutrients, and immune substances (sIgA and lactoferrin) were measured using specialized analyzers and ELISA kits. The pH of the samples was determined at 24 and 48 hours using a tabletop pH analyzer.

Small but statistically significant changes were observed in several components during 48 hours of storage. Fat, carbohydrates, calcium, inorganic phosphorus, sIgA, and lactoferrin showed slight variations, while protein and zinc remained stable. Fat decreased after 24 hours compared with immediately after pasteurization but did not decline further at 48 hours. The mean pH increased slightly from 7.047 to 7.102 (p = 0.003). No bacterial growth was detected at either 24 or 48 hours.

Although minor biochemical changes occurred, these were not clinically significant. Extending PDHM use to 48 hours after thawing maintained its nutritional and microbiological integrity and could inform revisions to current Japanese milk bank guidelines.

Pasteurized donor human milk (PDHM) is widely recommended for preterm infants when their mother’s own milk is unavailable. Storage duration of frozen PDHM varies across countries. In Japan, PDHM is stored at −30 °C; however, there is no information on whether long-term storage at −30 °C affects PDHM quality.

This study aimed to determine the effects of freezing at −30 °C for 6, 9, and 12 months after expression on bacterial growth and nutrient content of PDHM.

This was an experimental laboratory study of nutrient and bacterial stability over time. A total of 20 milk samples were pasteurized within 3 months after expression and stored at −30 °C. Bacterial counts and levels of macronutrients, minerals, secretory Immunoglobulin A (sIgA), and lactoferrin in PDHM were analyzed after pasteurization and at 6, 9 and 12 months after expression. A Friedman test followed by a Bonferroni-adjusted Wilcoxon signed-rank test was performed.

No bacteria were detected in the 20 samples after pasteurization or at any time point. When the concentrations of nutrients were compared to the values immediately after pasteurization, carbohydrates at 9 and 12 months and zinc at 12 months showed slight increases, but the respective increases were minimal (carbohydrate: +3.2% at 9 months and +3.8% at 12 months; zinc: +7.8% at 12 months). The concentrations of protein, fat, calcium, inorganic phosphorus, sIgA, and lactoferrin remained stable at 6, 9, and 12 months.

These results suggest that PDHM can be safely stored at −30 °C for 12 months after expression without compromising bacterial safety and nutritional quality.

Maternal satisfaction with breastfeeding is an important indicator of breastfeeding success. However, little is known about the satisfaction of women in lower-middle-income countries, whose breastfeeding rates tend to be higher than those in high-income countries.

To investigate the factors associated with maternal satisfaction with breastfeeding.

This is a cross-sectional and observational study with 291 women in the 6 months postpartum, all users of the public health network in the city of Aracaju, Brazil. Data were collected using the Maternal Breastfeeding Evaluation Scale, along with a semi-structured questionnaire covering demographic, pregnancy, childbirth, and postpartum characteristics. A multivariable logistic regression model with intra-block analysis was constructed to identify factors associated with maternal satisfaction with breastfeeding.

The average maternal satisfaction score was 125.3 (SD = 13.7). Higher maternal satisfaction was associated with lower monthly family income (less than half the minimum wage; OR = 2.12; 95% CI [1.20, 3.74]), absence of problems in breastfeeding (OR = 2.09; 95% CI [1.19, 3.67]), current exclusive breastfeeding (OR = 1.82; 95% CI [1.09, 3.04]), support in caring for the child (OR = 1.89; 95% CI [1.05, 3.40]), and good quality of maternal sleep (OR = 1.71; 95% CI [1.01, 2.90]).

Preventing breastfeeding problems and providing support in childcare, with a focus on improving maternal sleep quality, are essential to increasing breastfeeding satisfaction in low-resource women. These strategies are low-cost and feasible for implementation within routine health services.

In the United States, there are high rates of distribution and use of breast pumps. However, research on the environmental impact of the growing breast pump industry remains unexplored.

The aim of this study was to examine current recycling programs and environmental sustainability initiatives of breast pump companies whose products are commonly distributed in the United States. A secondary aim was to analyze the materials used to manufacture breast pumps and accessories that are pertinent to environmental considerations and human health.

We conducted a cross-sectional survey, using publicly available information on the companies’ websites and phone and/or email responses from breast pump company representatives.

Of 20 breast pump companies included in the analysis, one reported having a recycling program, and eight provided disposal recommendations on their websites. Three companies had stated environmental initiatives. Eighteen companies reported using polypropylene, silicone, and other plastics in their breast pumps and/or pump accessories, and two companies reported using acrylonitrile butadiene styrene.

In the United States, there is a lack of recycling programs and accessible information regarding recycling, environmental initiatives, and materials used in breast pumps and/or pump accessories. With the expansion of the U.S. breast pump industry, convenient and transparent information regarding recycling programs and environmental initiatives must be prioritized.