It is known that the fat content of breast milk is higher in hindmilk than in foremilk. However, it has not been determined if this increased fat content results from an increase in the number of milk fat globules (MFGs), an increase in the size of MFGs, or both. This study aims to determine which factor plays the most important role.

For preterm and very low birthweight infants, the mother’s own milk is the best nutrition. Based on the latest information for mothers who give birth to preterm and very low birthweight infants, medical staff should encourage and assist mothers to pump or express and provide their own milk whenever possible. If the supply of maternal milk is insufficient even though they receive adequate support, or the mother’s own milk cannot be given to her infant for any reason, donor human milk should be used. Donors who donate their breast milk need to meet the Guideline of the Japan Human Milk Bank Association. Donor human milk should be provided according to the medical needs of preterm and very low birthweight infants, regardless of their family’s financial status. In the future, it will be necessary to create a system to supply an exclusive human milk‐based diet (EHMD), consisting of human milk with the addition of a human milk‐derived human milk fortifier, to preterm and very low birthweight infants.

Background: Reducing the disposal of donated human milk (HM) is important for efficient management of human milk banks (HMBs). The presence of bacteria growth is the main factor that contributes to the disposal of donated HM. The bacterial profile in HM is suspected to differ between term and preterm mothers, with HM from preterm mothers containing more bacteria. Thus, elucidation of the causes of bacterial growth in preterm and term HM may help to reduce the disposal of donated preterm HM. This study compared the bacterial profiles of HM between mothers of term infants and mothers of preterm infants. Methods: This pilot study was conducted in the first Japanese HMB, which was initiated in 2017. This study analyzed 214 human milk samples (term: 75, preterm: 139) donated by 47 registered donors (term: 31, preterm: 16) from January to November 2021. Bacterial culture results in term and preterm HM were retrospectively reviewed in May 2022. Differences in total bacterial count and bacterial species count per batch were analyzed using the Mann–Whitney U test. Bacterial loads were analyzed using the Chi-square test or Fisher’s exact test. Results: The disposal rate did not significantly differ between term and preterm groups (p = 0.77), but the total amount of disposal was greater in the preterm group (p < 0.01). Coagulase-negative Staphylococci, Staphylococcus aureus, and Pseudomonas fluorescens were frequently found in both types of HM. Serratia liquefaciens (p < 0.001) and two other bacteria were present in term HM; a total of five types of bacteria, including Enterococcus faecalis and Enterobacter aerogenes (p < 0.001) were present in preterm HM. The median (interquartile range) total bacterial counts were 3,930 (435–23,365) colony-forming units (CFU)/mL for term HM and 26,700 (4,050–334,650) CFU/mL for preterm HM (p < 0.001). Conclusions: This study revealed that HM from preterm mothers had a higher total bacterial count and different types of bacteria than HM from term mothers. Additionally, preterm infants can receive nosocomial-infection-causing bacteria in the NICU through their mother’s milk. Enhanced hygiene instructions for preterm mothers may reduce the disposal of valuable preterm human milk, along with the risk of HM pathogen transmission to infants in NICUs.

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.