Background The purpose of this study was to evaluate the circadian variation of human milk macronutrients and energy content depending upon pregnancy duration. Methods One hundred eighty fresh human milk samples from 45 mothers (27 of preterm and 18 of full-term newborns) were collected on a single day chosen between the 14th to 16th day after delivery. The samples were taken four times per day at 12 PM, 6 PM, 12 AM and 6 AM. Only lactating women, who could not breastfeed their hospitalized newborns and expressed milk by breast pump, were enrolled in the study. Human milk macronutrient composition and energy count were evaluated by mid-infrared spectrophotometry. Results Significant differences in macronutrient content were observed between 6 AM and 12 PM for mean protein content (t = − 4.62, df = 44, p < 0.001), for mean fat content (t = − 2.10, df = 44, p = 0.04) and for mean energy content (t = − 2.24, df = 44, p = 0.03); between 6 AM and 6 PM for mean protein content (t = − 2.41, df = 43, p = 0.02), for mean fat content (t = − 3.76, df = 43, p = 0.001) and for mean energy content (t = − 3.85, df = 43, p < 0.001); between 12 PM and 12 AM for mean protein content (Wilcoxon test V = 75.5, p = 0.001), for mean fat content (t = 2.50, df = 44, p = 0.02) and for mean energy content (t = 2.74, df = 44, p = 0.01); between 6 PM and 12 AM for mean protein content (V = 229, p = 0.02), for mean fat content (t = 4.39, df = 43, p < 0.001) and for mean energy content (t = − 4.57, df = 43, p < 0.001). The average content of carbohydrates did not change significantly during the 24 h. The samples of preterm newborns’ mothers had more apparent diurnal fluctuations in macronutrient content. Conclusions Our study revealed significant diurnal variations in protein and fat in human milk, and these circadian fluctuations were more apparent in the milk of mothers of preterm infants.

Introduction: Human donor milk is widely used to feed premature and sick newborns when the milk of their own mothers is insufficient. All treatment processes involving human milk affect its composition. The aim of this study was to assess changes in the macronutrients and bioactive protein (lactoferrin and lysozyme) content in human milk caused by freezing and Holder pasteurization. Materials and Methods: Milk samples were collected from 42 mothers 14-16 days after delivery. Each sample was divided into two parts and tested twice for macronutrient content, once upon being freshly collected and again after freezing at-40°C, thawing and Holder pasteurization. The lysozyme and lactoferrin concentrations were first determined in the unpasteurized thawed human milk after it was stored frozen at-80°C for up to 10 months and again after Holder pasteurization. The macronutrient concentrations were determined by midinfrared spectrophotometry, and enzyme-linked immunosorbent assay was used to measure the lysozyme and lactoferrin concentrations. Results: Freezing and Holder pasteurization had no significant effects on the macronutrient concentrations. The mean lactoferrin content before and after pasteurization was 2.5-1.07 and 0.03-0.03 mg/mL, respectively (p < 0.001), and the lysozyme content was 19.57-20.11 and 12.62-14.14 lg/mL, respectively (p = 0.007). Conclusions: Freezing and Holder pasteurization did not decrease the nutritional value of human milk but caused considerable loss of lactoferrin and lysozyme. New methods for treating human milk are needed that ensure the destruction of pathogenic microorganisms while retaining the biological and nutritional value of the milk. The Clinical Trial Registration number: NCT04382989.

Motinos pienas unikalus ne tik dėl savo sudėties, bet ir dėl to, kad jo sudėtis nuolat kinta, prisitaikydama prie individualių naujagimio poreikių. Straipsnyje aprašomas 2,5 metų Vilniaus universiteto ligoninės Santaros klinikų Neonatologijos centre vykdytas motinos pieno sudėties tyrimas, analizuojami veiksniai, turintys įtakos motinos pieno sudėčiai, bei galima klinikinė motinos pieno pokyčių reikšmė.

Acute kidney injury is associated with mortality of very low birth weight infants and reduces their survival regardless of other factors. The kidneys in the extremely preterm infants are very immature and susceptible to environmental factors. Clinical conditions and medications are risk factors for acute kidney injury in these patients. Nephrolithiasis in preterm infants is an extremely rare phenomenon that usually manifests as a complication of nephrocalcinosis. This is a case report that describes several episodes of acute kidney injury in the first two months of age in an extremely low birth weight infant with kidney stones in the background. The main causes that led to acute kidney injury in this patient were persistent ductus arteriosus, sepsis and captopril. At one month of age, ultrasound detected calcinates in the right kidney. Within two weeks a large number of linear stones formed across the collecting duct system. Small calcinates still remained in the right kidney when the girl was half a year of the corrected age. The evaluation of a neonate who develops acute kidney injury requires a systematic approach. Early identification of the emerging risk factors and prevention of nephrolithiasis along with effective treatment can reduce the risk of developing acute kidney injury in very low birth weight infants.