Perinatal intermittent hypoxia increases early susceptibility to ANG II-induced hypertension in adult male but not in female Sprague-Dawley rats.

Prenatal, perinatal, and adulthood exposure to chronic intermittent hypoxia (IH) increases blood pressure in rodents. Males exposed to chronic IH have higher blood pressure versus females. However, it is unknown if this same-sex difference exists with acute perinatal IH. We tested the hypothesis that acute perinatal IH increases baseline blood pressure and enhances sensitivity to angiotensin II (ANG II)-induced hypertension in male Sprague-Dawley rats. Male and female pups were randomized to control (room air) or IH (10 min of ∼10% O2 for 3 times/day) for the first 8 days of life. IH decreased oxygen saturation, as confirmed via a pulse oximeter. Pups were weaned at postnatal day 21. Blood pressure was measured via telemetry beginning at 14 wk of age and analyzed separately into light and dark phases to assess circadian rhythm. Osmotic minipumps to deliver ANG II were implanted at 15 wk of age. Perinatal IH exposure did not alter baseline blood pressure. One week of ANG II treatment increased blood pressure in light and dark periods in males exposed to IH versus control; there was no effect in females. Blood pressure among the groups was comparable following 2 wk of ANG II infusion. Perinatal IH did not change the circadian rhythm. Following ANG II treatment, indexes of renal injury were measured. Perinatal IH did not alter kidney size, structure, nephron number, or creatinine clearance. These data indicate that acute perinatal IH enhances early ANG II-induced hypertension in males, independent of nephron loss or decreases in body weight or kidney function.NEW & NOTEWORTHY The impact of acute intermittent hypoxia (IH) in early life on blood pressure in adulthood is unknown. This study used a new model exposing female and male rat pups to acute IH in the first 8 days of life, without exposing the dam. Although baseline blood pressure was not altered in adulthood, IH increased susceptibility to angiotensin II hypertension only in males, supporting increased susceptibility of males exposed to IH to a second cardiovascular stressor.

Routine Diaper Change Alters Kidney Oxygenation in Premature Infants: A Non-A Priori Analysis.

BACKGROUND: Reduction in oxygen delivery to developing kidneys of premature infants may be an important source for acute kidney injury in premature infants. PURPOSE: To describe changes in continuous kidney oxygenation (RrSO 2 ) measures before, during, and after routine diaper changes. METHODS: Non-a priori analysis of a prospective cohort that received continuous measurement of RrSO 2 with near-infrared spectroscopy (NIRS) over the first 14 days of life demonstrating acute RrSO 2 drops surrounding diaper changes. RESULTS: In total, 26 of 38 (68%) infants (≤1800 g) from our cohort exhibited acute drops in RrSO 2 that temporally correlated with diaper changes. Mean (SD) RrSO 2 baseline prior to each diaper change event was 71.1 (13.2), dropped to 59.3 (11.6) during diaper change, and recovered to 73.3 (13.2). There was a significant difference between means when comparing baseline to diaper change ( P < .001; 95% CI, 9.9 to 13.8) and diaper change to recovery ( P < .001; 95% CI, -16.9 to -11.2). The mean decrease in RrSO 2 during diaper change averaged 12 points (17%) below 15-minute RrSO 2 mean prior to diaper change, with quick recovery to prediaper change levels. No decreases in SpO 2 , blood pressure, or heart rate were documented during the intermittent kidney hypoxic events. IMPLICATIONS FOR PRACTICE AND RESEARCH: Routine diaper changes in preterm infants may increase the risk for acute reductions in RrSO 2 as measured by NIRS; however, the impact on kidney health remains unknown. Larger prospective cohort studies assessing kidney function and outcomes related to this phenomenon are needed.

Late-Onset Hyponatremia in Premature Infants.

Late-onset hyponatremia (LOH) frequently affects premature infants 2 or more weeks of age due to inadequate sodium intake and excessive kidney loss. Late-onset hyponatremia typically occurs in infants who are physiologically stable and is defined as serum sodium of 132 mEq/L or less or between 133 and 135 mEq/L if receiving sodium supplementation. Recent evidence suggests that spot urine sodium levels may improve the recognition of LOH, as low levels of excreted urine reflect a total body sodium deficit and negative balance. Untreated LOH may result in poor somatic growth, neurodevelopmental delay, higher incidence of bronchopulmonary dysplasia, and more severe retinopathy of prematurity. The primary prevention of LOH is to maintain serum sodium between 135 and 145 mEq/L; however, there are currently no formal protocols guiding sodium supplementation. The purpose of this article is to present on overview of LOH pathophysiology and its effect on somatic growth, neurodevelopment outcomes, and other related sequelae. We further discuss general management strategies and describe a protocol for sodium supplementation that is presently undergoing an evaluation for effectiveness.

Renal Oxygenation (rSO 2 ) Population Parameter Estimates in Premature Infants Routinely Monitored With Near-Infrared Spectroscopy.

BACKGROUND: Currently, reference ranges for renal oxygenation measured by near-infrared spectroscopy (NIRS) in preterm infants beyond the first days of life are lacking, especially those born prior to 29 weeks' gestation. Population estimates of renal oxygenation (rSO 2 ) levels among preterm infants over time have yet to be established, leading to reluctance in clinical application. PURPOSE: To characterize the distribution and estimate population parameters for renal oxygenation measured by NIRS during the first 14 days of life among preterm infants. METHODS: We prospectively observed rSO 2 trends of 37 infants before 34 weeks' gestation and 1800-g or less birth weight for the first 14 days of life. Analyses included distribution fit tests, ordinary least squares (OLS) regression, and t tests. RESULTS: Average daily rSO 2 variation steadily increased with 42% difference through the first 14 days of life. For all infants, renal rSO 2 means peaked during the first 3 days of life and plateaued around 7 days. Daily rSO 2 slopes were significantly lower among males and infants 29 weeks' or less gestation. IMPLICATIONS FOR PRACTICE: Renal rSO 2 during the first 14 days of life reflects normal extrauterine transition reaching stabilization around 7 days of life. Gestational age, birth weight, and gender may predict the early trajectory of rSO 2 patterns. Population estimates provide parameters for renal rSO 2 that may indicate early-onset tissue hypoxia when acute or significant drops from baseline occur. IMPLICATIONS FOR RESEARCH: We present a framework to guide future research using renal NIRS technology in preterm infants to determine deviations from expected trends that may precede renal injury.

Renal Oxygenation Measured by Near-Infrared Spectroscopy in Neonates.

BACKGROUND: Acute kidney injury (AKI) affects approximately 30% of infants admitted to the neonatal intensive care unit (NICU), and increases mortality risk by 50%. Current diagnostic criteria (serum creatinine rise with oliguria) cannot detect early-onset AKI, as up to 50% of nephron damage may occur by the time these abnormalities present. Once AKI is established, clinical management is often ineffective; therefore, prevention is key. Near-infrared spectroscopy (NIRS) offers a feasible, noninvasive approach to continuously monitor renal oxygenation trends over time, serving as a surrogate marker for renal perfusion. PURPOSE: To provide an overview of NIRS principles for measuring renal oxygenation, and to describe current evidence of how this technology is being used among infants admitted to the NICU relative to the prediction and identification of AKI. METHODS: A comprehensive search of PubMed and CINHAL focused on renal NIRS studies in NICU preterm and term infants was conducted. RESULTS: Findings from 34 studies were included. In term infants, reduced renal oxygenation correlated to invasive SvO2 monitoring, predicted survivability and AKI. In preterm infants, reduced renal oxygenation was associated with AKI in one study, yet contrasting findings were reported in those with patent ductus arteriosus, including those who received prostaglandin inhibitors. Normative data in all infants were sparse. IMPLICATIONS FOR PRACTICE: Renal NIRS may offer a noninvasive measurement of kidney hypoperfusion that may precede conventional diagnostic measures. IMPLICATIONS FOR RESEARCH: Normative data are lacking, the threshold for renal ischemia is not defined, and consensus guiding clinical treatment based on NIRS data is nonexistent.

Neonatal Microbiome and Its Relationship to Necrotizing Enterocolitis: A Review of the Science.

Necrotizing enterocolitis (NEC) occurs in many premature infants hospitalized in the neonatal intensive care unit. About 3% to 15% of very low-weight premature infants develop NEC, with an estimated 30% mortality rate for the cases requiring surgery. Currently, there is no known pathogenesis for NEC in the patient's populations. However, one of the most widely accepted hypotheses is having an abnormal fetal gut microbiome. The purpose of this review is to discuss some current methods of dysbiosis in the neonatal microbiome, such as maternal health, breastfeeding, and delivery method, and then to connect these to the occurrence of NEC in the infant and finally discuss some possibilities for limiting the occurrence of NEC in the future.

NICU Maternal-Infant Bonding: Virtual Visitation as a Bonding Enhancement Tool.

The admission of an infant to the neonatal intensive care unit (NICU) presents specialized barriers to the maternal-infant bonding (MIB) process. Virtual visitation (VV) provides a mother with the opportunity to have continual access to her hospitalized infant via a one-way live Web camera. While increasingly used in the NICU, VV remains a novel concept. The objective of this study was to introduce a conceptual model that incorporates the use of VV into the NICU MIB process. Adapted from the Model of Mother-Infant Bonding After Antenatal HIV Diagnosis, a newly developed model of MIB using VV as a bonding enhancement tool is offered. A Model of NICU Maternal-Infant Bonding Incorporating Virtual Visitation presents the NICU bonding process in a chronological manner, with 5 primary propositions and an explanation of their related themes. Virtual visitation is introduced into the bonding process and is shown to act as a moderated variable. A Model of NICU Maternal-Infant Bonding Incorporating Virtual Visitation introduces VV as a tool to enhance the MIB process that occurs in the NICU. The model provides the basis for the development of a research program to examine the multiple potential effects of VV in the NICU.

Influences of Maternal Prepregnancy Obesity and Gestational Diabetes Mellitus on the Infant Gut Microbiome in Full-Term Infants.

This review examines the current evidence of how prepregnancy obesity (PPO) and gestational diabetes mellitus (GDM) influence the newborn gut microbiome. Scientific gaps in the literature are described to guide future research in this area. The prevalence of PPO and GDM increased to 64% in the United States over the past decade. Prepregnancy obesity and GDM influence newborn gut microbiome and contribute to adverse short- and long-term outcomes in full-term infants. This review aims to discuss current research findings related to the associations between PPO and GDM, separately, and together, on infant gut microbiome outcomes, provide an overview of short-term and long-term outcomes, describe clinical relevance, and identify avenues for future scientific inquiry. This review found that PPO and GDM influence infant gut microbiomes. Infants born to women with PPO and GDM were found to have lower levels of diversity in gut microbiota than infants born to normal prepregnancy weight women and those born to women without GDM.

Does red blood cell irradiation and/or anemia trigger intestinal injury in premature infants with birth weight ≤ 1250 g? An observational birth cohort study.

BACKGROUND: Necrotizing enterocolitis (NEC) is a leading cause of neonatal morbidity and mortality in premature infants. To date, no effective biomarkers exist to predict which premature infants will develop NEC, limiting targeted prevention strategies. Multiple observational studies have reported an association between the exposure to red blood cell (RBC) transfusion and/or anemia and the subsequent development of NEC; however, the underlying physiologic mechanisms of how these factors are independently associated with NEC remain unknown. METHODS: In this paper, we outline our prospective, multicenter observational cohort study of infants with a birth weight ≤ 1250 g to investigate the associations between RBC transfusion, anemia, intestinal oxygenation and injury that lead to NEC. Our overarching hypothesis is that irradiation of RBC units followed by longer storage perturbs donor RBC metabolism and function, and these derangements are associated with paradoxical microvascular vasoconstriction and intestinal tissue hypoxia increasing the risk for injury and/or NEC in transfused premature infants with already impaired intestinal oxygenation due to significant anemia. To evaluate these associations, we are examining the relationship between prolonged irradiation storage time (pIST), RBC metabolomic profiles, and anemia on intestinal oxygenation non-invasively measured by near-infrared spectroscopy (NIRS), and the development of NEC in transfused premature infants. DISCUSSION: Our study will address a critical scientific gap as to whether transfused RBC characteristics, such as irradiation and metabolism, impair intestinal function and/or microvascular circulation. Given the multifactorial etiology of NEC, preventative efforts will be more successful if clinicians understand the underlying pathophysiologic mechanisms and modifiable risk factors influencing the disease. TRIAL REGISTRATION: Our study is registered in ClinicalTrials.gov Identifier: NCT02741648 .

Mesenteric Oxygenation Changes Associated With Necrotizing Enterocolitis and Pneumoperitoneum After Multiple Blood Transfusions: A Case Report.

BACKGROUND: The multifactorial pathology and broad clinical presentation of necrotizing enterocolitis (NEC) development in premature infants make prediction of disease onset extremely challenging. Over the past decade, packed red blood cell (PRBC) transfusions have been temporally linked to the development of NEC in severely anemic preterm infants, although this issue is highly controversial. PURPOSE: In this case study, we describe events of an extremely low birth-weight infant who developed NEC complicated by pneumoperitoneum after receiving multiple PRBC transfusions. Specifically, we describe mesenteric tissue oxygenation trend changes as measured by continuous near-infrared spectroscopy (NIRS) technology. METHODS: As part of a larger prospective, observational investigation, this infant was monitored with NIRS (INVOS 5100C; Medtronic, Boulder, Colorado) before, during, and 48 hours following PRBC transfusions. RESULTS: The infant demonstrated severe, prolonged, and persistent reductions in mesenteric tissue oxygenation following blood transfusions, yet routine physiologic monitoring did not indicate intestinal hypoperfusion or impending NEC onset. IMPLICATIONS FOR PRACTICE: This report demonstrates the ability of NIRS to capture possible tissue ischemia during early stages of NEC that may help guide bedside therapeutic interventions. IMPLICATIONS FOR RESEARCH: Larger cohort studies to evaluate the ability of NIRS to capture early tissue ischemia are essential to validate the feasibility of adding this technology as a routine clinical bedside tool.Video Abstract available at https://journals.lww.com/advancesinneonatalcare/Pages/videogallery.aspx.

Urinary Biomarkers to Predict Neonatal Acute Kidney Injury: A Review of the Science.

Acute kidney injury (AKI) occurs in approximately 30% of all infants hospitalized in the neonatal intensive care unit. About 40% of very low-birth-weight infants develop AKI, with an estimated mortality rate of 50% to 80%. Very low-birth-weight survivors have twice the risk of developing chronic renal disease later in life compared with their term counterparts. Current diagnostic modalities for AKI include serum creatinine and urine output; however, recent studies suggest that these measures are imprecise, as they may not change until 25% to 50% of renal function is lost. Urinary biomarkers may more accurately identify infants at risk for early AKI development. The purpose of this review is to discuss current research findings related to neonatal AKI risk factors, provide an overview of short- and long-term outcomes, describe innovative diagnostic approaches, and identify future research direction needed to improve prediction and intervention strategies associated with renal impairment.

Understanding the Biologic Therapies of Probiotics, Prebiotics, and Synbiotics: Exploring Current Evidence for Use in Premature Infants for the Prevention of Necrotizing Enterocolitis.

Necrotizing enterocolitis remains a significant cause of morbidity and mortality in very low-birth-weight infants (<1500 g), with current preventive strategies unclear. Scientific evidence has recently emerged, suggesting that probiotics, prebiotics, and synbiotics may effectively and safely alter the premature intestinal microbiota, enhancing a deficient innate immune response and maturing the intestinal barrier to prevent necrotizing enterocolitis development. Currently, formal recommendations do not support routine use of these dietary supplementations for premature infants. Here, we examine how probiotic, prebiotic, and synbiotic preparations physiologically alter the underdeveloped intestinal microbial environment to potentially reduce necrotizing enterocolitis incidence and discuss current evidence that has examined safety and efficacy factors potentially supporting routine use among the premature infant population.

Feeding preterm infants during red blood cell transfusion is associated with a decline in postprandial mesenteric oxygenation.

OBJECTIVE: To evaluate the mesenteric tissue oxygenation response in preterm infants fed and not fed during red blood cell (RBC) transfusions. STUDY DESIGN: Prospective, observational comparison of mesenteric oxygenation using near-infrared spectroscopy in preterm infants (<33 weeks' at birth) who were fed or not fed during RBC transfusion. Tissue oxygenation means were examined up to 48 hours after each transfusion event. RESULTS: Mean mesenteric regional oxygen saturation (rSO2) slopes during RBC transfusion of fed (n = 9) vs not fed (n = 8) infants ranged from -0.23 to +0.23 (mean 0.04) with no differences between groups (P = .480). However, following transfusions, postprandial mesenteric oxygenation means significantly declined in infants fed during transfusion compared with infants not fed during transfusion (P < .001). Infants fed during RBC transfusion had a mean 2.16 point decrease in rSO2 mesenteric oxygenation with each sequential feeding post-transfusion, whereas infants not fed during RBC transfusion increased their rSO2 postprandial mesenteric oxygenation by a mean of 2.09 points. CONCLUSIONS: Mesenteric tissue oxygenation during RBC transfusion is not influenced by feeding status. However, infants fed during RBC transfusion had, for the next 15 hours, decreasing postprandial mesenteric tissue oxygenation patterns compared with infants not fed during RBC transfusion. Feeding during RBC transfusions may increase the risk for mesenteric ischemia and the development of transfusion-related necrotizing enterocolitis in preterm infants.

Understanding Near-Infrared Spectroscopy: An Update.

Near-infrared spectroscopy (NIRS) is a novel technology that uses infrared light to noninvasively and continuously measure regional oxygen extraction in real time at the bedside. Neonatal research using this device supports its use as an adjunct to routine cardiovascular monitoring because NIRS serves as a surrogate marker for end-organ perfusion and can detect minute changes in cerebral, intestinal, and kidney tissue beds. Multiple conditions affecting premature infants are frequently associated with hypoperfusion; therefore, methods to detect early tissue-specific perfusion alterations may substantially improve the clinician's ability to intervene and prevent further deterioration.

Red blood cell transfusion-related necrotizing enterocolitis in very-low-birthweight infants: a near-infrared spectroscopy investigation.

BACKGROUND: Recent evidence suggests that antecedent red blood cell (RBC) transfusions increase the risk for necrotizing enterocolitis (NEC), the most common gastrointestinal emergency encountered by very-low-birthweight (VLBW) infants. The underlying mechanism for this association is unknown. Altered oxygenation of the mesenteric vasculature during RBC transfusion has been hypothesized to contribute to NEC development and was investigated in this study. STUDY DESIGN AND METHODS: Oxygenation patterns among four VLBW infants who developed transfusion-related NEC (TR-NEC) were compared to four VLBW infants with similar gestational age who were transfused but did not develop NEC (non-NEC). Cerebral and mesenteric patterns were recorded before, during, and 48 hours after RBC transfusion using near-infrared spectroscopy (NIRS) technology. Percentage change from mean baseline regional oxygen saturation values and cerebrosplanchnic oxygenation ratios were analyzed. RESULTS: All TR-NEC infants (24-29 weeks' gestation; 705-1080 g) demonstrated greater variation in mesenteric oxygenation patterns surrounding transfusions than non-NEC infants (27.6-30 weeks' gestation; 980-1210 g). TR-NEC infants received larger mean volumes of total blood (27.75 ± 8.77 mL/kg) than non-NEC infants (15.25 ± 0.5 mL/kg). CONCLUSION: Wide fluctuation and decreases in mesenteric oxygenation patterns are more pronounced in TR-NEC infants, especially before TR-NEC onset, compared to non-NEC infants. Greater total volume of infused blood was associated with TR-NEC in preterm infants. Using NIRS, larger prospective studies are needed to further evaluate potential risk factors for NEC in this high-risk population.

Transfusion-related necrotizing enterocolitis: a conceptual framework.

Necrotizing enterocolitis (NEC) is a disease primarily of prematurity characterized by partial or entire gut necrosis and is associated with significant mortality and morbidity. Recent studies report that approximately 25% to 35% of very low-birth-weight infants less than 1500 g receiving packed red blood cell transfusions develop temporally associated NEC, known as transfusion-related NEC (TR-NEC). Although there are many known risk factors for NEC, this article focuses on 3 contributing factors: packed red blood cell transfusions, enteral feedings, and gastrointestinal immaturity. Previous data suggest that these factors may interact to affect neonatal intestinal tissue oxygenation, which may lead to tissue ischemia, resulting in intestinal injury. This article presents a conceptual framework that combines current theoretical perspectives for TR-NEC, and reviews previous research examining related variables and how their interaction may increase the risk for TR-NEC development. In addition, incorporation of the proposed framework to guide future research and nursing care in this area is discussed.

Novel multinutrient human milk-based human milk fortifier promotes growth and tolerance in premature infants.

BACKGROUND: The objective of this study was to determine whether human milk supplemented with a novel human milk-based human milk fortifier (Novel HMF), compared with a bovine milk-based HMF (Bovine HMF), supports preterm infant growth through 36 weeks' postmenstrual age (PMA). METHODS: This single-center, prospective trial compared growth and nutrition outcomes of preterm infants provided a human milk-based diet (mother's own milk or donor milk) supplemented with a Novel HMF with historic controls provided Bovine HMF. Preterm infants with an estimated gestational age (EGA) between 23 and 33 weeks' PMA and birth weight between 750 and 1800 g were eligible for study inclusion. Weight, length, and head circumference (HC) were monitored weekly. The occurrence of late-onset sepsis, nil per os (NPO) days, necrotizing enterocolitis, metabolic acidosis, and serious adverse events were monitored. RESULTS: Birth weight, length, HC, and EGA were similar between the Novel HMF (n = 37) and Bovine HMF (n = 49) groups. The days to regain birth weight was shorter in the Novel HMF group (9.4 ± 4.0 vs 11.4 ± 4.8, P = .0343), with similar weight gain (g/day) from birth to 36 weeks' PMA. Adjusted weight growth velocity (g/kg/day) was significantly higher in the Novel HMF group at 14 and 21 days but similar at 36 weeks' PMA. The Novel HMF group experienced fewer NPO days with a similar total number of feeding days. CONCLUSIONS: A novel, multinutrient, human milk-based HMF is well tolerated and meets the nutrition needs of preterm infants.

Understanding near-infrared spectroscopy.

Near-infrared spectroscopy (NIRS) is a noninvasive technique that monitors regional tissue oxygenation reflecting perfusion status. Near-infrared spectroscopy has the ability to continuously and simultaneously monitor tissue perfusion in different organ systems at the bedside without interrupting routine care. Research has demonstrated its benefit in monitoring cerebral, intestinal, and renal perfusion to detect potential ischemic episodes. Near-infrared spectroscopy can augment current physiologic monitoring to increase awareness of abnormal perfusion status in the preterm population and potentially reduce risks associated with many diseases that may lead to ischemic injury. This article provides an overview describing NIRS technology and function, its current use in neonatology, and pertinent research findings illustrating its benefit in the neonatal population. Near-infrared spectroscopy may evolve into an important diagnostic and prognostic tool for neonatal treatment and outcome.

Review of Preterm Human-Milk Nutrient Composition.

BACKGROUND: The human milk-fed preterm infant is at risk for growth failure, micronutrient deficiencies, and neurocognitive delay. Although protective and better tolerated than formula, human milk alone cannot meet the high nutrient requirements of this population, and fortification is necessary. Clinicians use assumptions of preterm human-milk composition to determine the type and quantity of fortification. OBJECTIVES: The objectives of this review were to identify evidence of macronutrient and micronutrient concentration in preterm human milk and to identify knowledge gaps regarding composition. METHODS: PubMed and the Cumulative Index to Nursing and Allied Health Literature were used to identify original articles published between January 1950 and December 2019. RESULTS: Twenty-seven articles were found containing original data on macronutrients and micronutrients. Most (67%) of the studies published after 2011 measured the macronutrients and included gestational ages from 28 to 36 weeks. Milk collection methods, experimental design, and analytical methods varied between studies. There are 15 countries represented in this review; all of the American studies (n = 7) were published from 1980 to 1984. CONCLUSIONS: African American women, or women delivering before 28 weeks' gestation are not represented in the literature. Accurate and targeted human-milk fortification depends on comprehensive, complete, and representative human-milk nutrient data. We have aggregated all available preterm human-milk macronutrient and micronutrient data and reported trends associated with lactation stage and gestational age. This report can aid in the design of feeding plans that are appropriate for the gestational age of the preterm infant and the lactation stage of the breastmilk.

Nutrient composition of preterm mother's milk and factors that influence nutrient content.

BACKGROUND: Breast milk feedings are the optimal feeding choice for premature infants. Clinicians depend on accurate nutrient profiles of the breast milk in order to make informed decisions regarding the need for nutrient supplementation. Existing data for nutrient composition of preterm breast milk are dated and not representative of the current population of women delivering prematurely in the United States. OBJECTIVES: The purpose of this prospective, longitudinal, single-center observational study was to measure the macronutrient and micronutrient composition of breast milk expressed by mothers, including women who self-identify as black, delivering preterm infants at ≤33 completed weeks of gestation. METHODS: We collected breast milk samples from mothers of preterm infants admitted to the neonatal intensive care unit at Augusta University Medical Center from January 2019 through November 2019. Mother's milk samples were collected on postpartum days 7, 14, 21, and 28 and analyzed for macronutrients (energy, fat, protein, and carbohydrates) and micronutrients (sodium, potassium, chloride, calcium, phosphorus, magnesium, vitamin D, and zinc). RESULTS: Thirty-eight mothers, mean age 27 ± 5.1 y and majority black (66%), provided milk for the study. The mean estimated gestational age and birth weight were 28.2 ± 2.8 weeks of gestation and 1098 ± 347 g, respectively, with 42% of mothers in the cohort delivering before week 28 of pregnancy. Differences in protein, sodium, potassium, calcium, phosphorus, and zinc concentrations based on race, day, and milk volume were identified. Dilution effects for protein, sodium, chloride, and vitamin D concentrations over time were identified. CONCLUSIONS: Our study is among the first to characterize breast milk composition from women who delivered extremely preterm infants and adds to the evidence that race, gestational age, and volume influence the composition of preterm mother's milk. These factors should be considered when designing mother's milk-based feeds for premature infants.