Among exclusively breastfed infants, human milk (HM) provides complete nutrition in the first mo of life and remains an important energy source as long as breastfeeding continues. Consisting of digestible carbohydrates, proteins, and amino acids, as well as fats and fatty acids, macronutrients in human milk have been well studied; however, many aspects related to their relationship to growth in early life are still not well understood. We systematically searched Medline, EMBASE, the Cochrane Library, Scopus, and Web of Science to synthesize evidence published between 1980 and 2022 on HM components and anthropometry through 2 y of age among term-born healthy infants. From 9992 abstracts screened, 57 articles reporting observations from 5979 dyads were included and categorized based on their reporting of HM macronutrients and infant growth. There was substantial heterogeneity in anthropometric outcome measurement, milk collection timelines, and HM sampling strategies; thus, meta-analysis was not possible. In general, digestible carbohydrates were positively associated with infant weight outcomes. Protein was positively associated with infant length, but no associations were reported for infant weight. Finally, HM fat was not consistently associated with any infant growth metrics, though various associations were reported in single studies. Fatty acid intakes were generally positively associated with head circumference, except for docosahexaenoic acid. Our synthesis of the literature was limited by differences in milk collection strategies, heterogeneity in anthropometric outcomes and analytical methodologies, and by insufficient reporting of results. Moving forward, HM researchers should accurately record and account for breastfeeding exclusivity, use consistent sampling protocols that account for the temporal variation in HM macronutrients, and use reliable, sensitive, and accurate techniques for HM macronutrient analysis.

The human milk microbiome may contribute to the benefits of breastfeeding by providing bacteria to the infant gastrointestinal tract. Many women pump their milk, but the effect of pumping on the milk microbiome is unknown. Our objective was to determine the effects of pumping supplies on the pumped human milk microbiome. This was an in-home, randomized, crossover trial of 2 collection methods. Women (n = 52) pumped twice within 3.5 h, once with their own breast pumps and milk collection supplies (OWN SUPP) and once with a hospital-grade pump and sterile collection supplies (STER SUPP). Pumping order was randomized. The milk microbiome was characterized by aerobic culturing and 16S ribosomal RNA gene sequencing. Milk collected with OWN SUPP yielded more total aerobic and gram-negative bacteria than milk collected with STER SUPP, reflecting a 6.6 (adjusted OR; 95% CI: 1.7, 25; P = 0.006) higher odds of containing >10⁴ total aerobic CFU/mL and 19 (adjusted OR; 95% CI: 4.1, 88; P < 0.0001) higher odds of yielding culturable gram-negative bacteria. Milk collected with OWN SUPP yielded more Proteobacterias , including higher relative abundances of Acinetobacter and Stenotrophomonas, compared to milk collected with STER SUPP. Results were consistent across pumping-order groups. We demonstrated that pumping supplies altered the milk microbiome. On average, milk collected with OWN SUPP resulted in elevated levels of culturable total and gram-negative bacteria and proteobacterial DNA compared to milk collected with STER SUPP. More research is needed to assess implications for infant health.

Acinetobacter bereziniae , formerly Acinetobacter genomospecies 10, is an opportunistic pathogen possessing resistance to multiple antibiotics, and it has been reported to be responsible for hospital-associated infections in immunocompromised individuals. We report the draft genome sequences of four Acinetobacter bereziniae strains that were isolated from a single human milk sample collected with a personal breast pump and a hand-washed milk collection kit.

Background: Necrotizing enterocolitis (NEC) remains a leading cause of morbidity and mortality in very low birthweight (VLBW) infants. Human milk feeding and standardized feeding protocols are protective, but clinical practice varies, particularly in fortifier choice. Whether human milk-derived fortifiers reduce NEC risk compared with cow milk-derived fortifiers remains unclear. Methods: We conducted a systematic state-of-evidence review and meta-analysis, searching PubMed, Web of Science, and Scopus through July 2025. Eligible studies included RCTs and observational cohorts of VLBW infants comparing an exclusive human milk diet (EHMD) including human milk-derived fortifiers to cow milk-derived diets. Two reviewers independently screened and extracted data. Both RCTs and observational studies were included to evaluate consistency of effect estimates across designs and to account for heterogeneity in control group feeding practices. Pooled odds ratios (ORs) with 95% CIs were calculated using a Sidik–Jonkman random-effects model. Sensitivity analyses by study design and exclusion of infant formula from controls were performed. Results: Twenty studies (five RCTs, 15 observational; n = 6794 infants) met inclusion criteria, most enrolling infants born ≤1250 g. Compared with cow milk-containing diets, EHMD was associated with lower odds of Bell Stage ≥ 2 NEC (OR: 0.59; 95% CI: 0.42, 0.81; p < 0.001; n = 4625) and surgical NEC (OR: 0.43; 95% CI: 0.32, 0.58; p < 0.0001; n = 4754). In direct comparisons of fortifier type with a base diet of human milk, estimates suggested lower odds of Bell Stage ≥ 2 NEC by 35% (OR: 0.65; 95% CI: 0.44, 0.97; p = 0.03, n = 2102) and surgical NEC by 49% (OR: 0.51; 95% CI: 0.26, 0.98; p = 0.04; n = 1659) with human milk-derived fortifiers. Effect estimates were generally consistent across study designs, although precision and statistical significance varied. Conclusions: EHMD with human milk-derived fortifiers was associated with lower odds of medical and surgical NEC in VLBW infants, with most evidence from infants born ≤1250 g, reflecting current clinical use in the highest-risk population. Although the number and sample sizes of RCTs remain limited, the consistency of effect estimates across both RCTs and observational studies, together with significance of pooled analyses, strengthens confidence in these findings. Pragmatic and registry-based studies using standardized fortification protocols may provide the most efficient pathway to strengthen the evidence base.

An exclusive human milk diet (EHMD) has been shown to reduce health complications of prematurity in infants born weighing ≤1250 grams compared to cow milk-based diets. Accordingly, the number of available human milk (HM)-based nutritional products continues to increase. Newly available products, and those reportedly soon to enter the market include homogenized donor human milk (DHM) and homogenized HM–based fortifiers. Existing literature demonstrating the benefits of an EHMD, however, is limited to non-homogenized HM-based products. Herein, we summarize existing evidence on the impact of homogenization on HM, with a particular focus on changes to the macromolecular structure of the milk fat globule and its subsequent impact on digestion kinetics. We use these published data to create a conceptual framework for the potential implications of homogenized HM-based nutritional products on preterm infant health. Importantly, we underscore that the safety and efficacy of homogenized HM-based products warrant investigation.

Human milk (HM) harbors a unique microbiome that contributes to the development of the infant gastrointestinal microbiome and influences long-term health outcomes. While pumping and bottle-feeding HM are increasingly common, doing so may introduce exogenous bacteria, altering this microbial community. The extent to which real-world pumping and hygiene practices alter the HM microbial community remains inadequately characterized. We conducted a secondary analysis of 104 paired milk samples from 52 healthy women to investigate the associations between at-home pump hygiene practices and the HM microbiota. We compared samples expressed with personal equipment, allowing women to follow their typical practices, noting variations in breast pump types (closed- vs. open-systems), pre-pumping handwashing, and collection kit cleaning practices (OWN). Milk was also expressed with hospital-grade pump with new, commercially sterilized equipment kits under study-controlled conditions (STER) to serve as a control representing each woman’s own unaltered milk microbiota. Microbiota composition was characterized using aerobic culture and 16S rRNA gene sequencing. Among OWN milk samples, personal breast pump type had little impact on the HM microbiota. Pre-pumping handwashing, practiced by only 22% of participants, was associated with lower bacterial counts. Compared to samples expressed with handwashed kits, those expressed using home-sterilized kits yielded fewer total and gram-negative bacterial counts, and lower relative abundances of Proteobacteria. The microbiota of OWN milk samples expressed with home-sterilized kits more closely resembled STER samples even in the absence of pre-pumping handwashing (R2 = 0.36; P < 0.001). At-home hygiene practices, particularly collection kit cleaning methods, substantially influence the HM microbiota. Home sterilization of collection kits may minimize changes to the HM microbiota during expression. These findings support evidence-based recommendations for hygienic pumping practices and underscore the need for further research on the health implications (if any) of pumping-dependent variations in the HM microbiota on infant health.