OBJECTIVES: To evaluate the growth, tolerance, and safety of a new ultraconcentrated liquid human milk fortifier (LHMF) designed to provide optimal nutrients for preterm infants receiving human breast milk in a safe, nonpowder formulation.
METHODS: Preterm infants with a body weight ≤1250 g fed expressed and/or donor breast milk were randomized to receive a control powder human milk fortifier (HMF) or a new LHMF for 28 days. When added to breast milk, the LHMF provided ∼20% more protein than the control HMF. Weight, length, head circumference, and serum prealbumin, albumin, blood urea nitrogen, electrolytes, and blood gases were measured. The occurrence of sepsis, necrotizing enterocolitis, and serious adverse events were monitored.
RESULTS: This multicenter, third party–blinded, randomized controlled, prospective study enrolled 150 infants. Achieved weight and linear growth rate were significantly higher in the LHMF versus control groups (P = .04 and 0.03, respectively). Among infants who adhered closely to the protocol, the LHMF had a significantly higher achieved weight, length, head circumference, and linear growth rate than the control HMF (P = .004, P = .003, P = .04, and P = .01, respectively). There were no differences in measures of feeding tolerance or days to achieve full feeding volumes. Prealbumin, albumin, and blood urea nitrogen were higher in the LHMF group versus the control group (all P < .05). There was no difference in the incidence of confirmed sepsis or necrotizing enterocolitis.
CONCLUSIONS: Use of a new LHMF in preterm infants instead of powder HMF is safe. Benefits of LHMF include improvements in growth and avoidance of the use of powder products in the NICU.
- BUN —
- blood urea nitrogen
- CO2 —
- carbon dioxide
- Hco3 —
- HMF —
- human milk fortifier
- LHMF —
- liquid human milk fortifier
- NEC —
- necrotizing enterocolitis
What’s Known on This Subject:
Current human milk fortifiers fail to provide the higher protein intake that is now recommended for feeding human milk–fed infants. There is a desire to avoid the use of powdered products when feeding these infants.
What This Study Adds:
A new ultraconcentrated liquid human milk fortifier that provides more protein than current powdered fortifiers is safe and supports better growth in human milk–fed infants than a powdered fortifier.
Feeding human milk to preterm infants provides immunologic benefits and reduces the risk of complications such as necrotizing enterocolitis (NEC) and sepsis1–3 compared with formula. However, human milk does not fully meet all of the nutritional needs of premature infants.4,5 Premature infants exclusively fed unfortified human milk have poorer growth rates compared with those fed either fortified human milk or premature infant formula6–9; hence, human milk fortifiers (HMFs) were introduced >20 years ago. The frequent lack of tolerance of enteral nutrition for weeks after birth combined with a high-protein turnover rate results in a cumulative protein and energy deficiency in many preterm infants. Currently marketed HMFs may fail to meet the increased protein needs of these infants.10,11 Furthermore, powdered HMFs also fail to meet the safety guidelines of the Academy of Nutrition and Dietetics and the Centers for Disease Control and Prevention for exclusion of powder formula from the NICU to decrease the risk of Cronobacter spp and other infectious complications.12,13 However, liquid human milk fortifiers (LHMFs) may dilute and thereby decrease the concentration of the beneficial host defense factors and bioactive components contained in human milk. Thus, there is a need to ultraconcentrate liquid fortifiers to balance these 2 needs.
Objectives of this study were to evaluate growth, tolerance, and safety with use of human breast milk fortified with new ultraconcentrated LHMFs that deliver higher protein than current powder fortifiers, comply with recommendations to avoid the use of powder formula in the NICU, and minimize the potential impact of diluting the beneficial components of human milk.
Premature infants with birth weight ≤1250g, gestational age ≤30 3/7 weeks, exclusively fed breast milk (mother’s milk or donor milk), and enteral intake of ≥80 mL/kg per day of unfortified human milk were eligible for this study. Exclusion criteria were: (1) underlying disease or congenital malformation likely to interfere with growth or tolerance of fortified human milk; (2) 5-minute Apgar score ≤4; (3) major surgery requiring anesthesia or diagnosis of grade 3 or 4 intraventricular hemorrhage before or on study day 0; (4) received pharmacologic doses of glucocorticoids for 3 consecutive days on or before study day 0; (5) consumed >3 feedings of fortified breast milk before study day 0; (6) feeding intolerance to human milk; (7) fluids restricted to <120 mL/kg per day; (8) history of creatinine >2 mg/dL on or during the 7 days before study day 0; (9) received probiotics; or (10) required >40% fraction of inspired supplemental oxygen via mechanical ventilation or continuous positive airway pressure on study day 0.
Institutional review boards at each study site reviewed and approved the protocol. A parent or guardian of each infant provided written informed consent. In addition, a data monitoring board was established to evaluate safety outcomes periodically throughout the study.
In this multicenter, third party–blinded, randomized controlled, prospective study, premature infants received breast milk fortified with 1 of 2 HMFs over a 28-day period. Eligible infants were stratified according to gender and birth weight (≤1000 g or >1000 g) and randomized on study day 0 to receive either powder HMF (control, Mead Johnson Nutrition) or LHMF (Mead Johnson Nutrition) for 28 days, hospital discharge, or termination of fortified breast milk feedings, whichever occurred first. Nutrient content of the study fortifiers is shown in Table 1; 4 packets of powder were mixed with 100 mL of preterm breast milk (control), and 5 vials of liquid were mixed with 100 mL of preterm breastmilk (LHMF) as a daily supply. When added to human milk, LHMF provides ∼20% more protein than the control powder does. Of note, the LHMF is in the form of hydrolyzed whey protein, which is acidic in nature. Both were added to breast milk at half strength on study day 1 and full strength on study day 2 and thereafter. After study day 14, either study fortifier could be increased to 26 calories/ounce and/or additional nutritional supplements could be given if growth was deemed inadequate by the attending neonatologist. Because this study was third party–blinded, those assessing outcomes were unaware of intervention assignments.
The primary study objective was to compare the rate of weight gain (grams/kilograms per day) of premature infants fed either a control powder or LHMF over a 28-day intervention period. Secondary outcomes measures were rate of length gain (linear growth), achieved growth (weight, length, and head circumference), ponderal index,14 enteral/parenteral nutritional intake, feeding tolerance, respiratory status, oliguria, serum chemistries, blood gases, incidence of NEC and sepsis, and serious adverse events.
Daily weights were obtained unclothed and without a diaper on the same electronically calibrated scale throughout the study. Body length and head circumference were measured to the nearest 0.5 cm or 0.25 inch once a week using a preterm infant length board and a flexible, nonstretchable cloth or vinyl tape, respectively.
Respiratory Outcomes, Morbidity, and Adverse Events
Suspected and/or confirmed NEC (determined by using modified Bell’s staging criteria for NEC) and sepsis were recorded.15 A subset of infants with a birth weight ≤1000 g was analyzed separately for NEC and sepsis. The occurrence of these and other serious adverse events was documented throughout the study.
Blood Collection and Laboratory Analysis
On study days 14 and 28, blood samples were drawn to measure blood urea nitrogen (BUN), carbon dioxide (CO2), bicarbonate (Hco3), sodium, potassium, chloride, albumin, calcium, creatinine, alkaline phosphatase, phosphorus, and prealbumin. We determined pH, Pco2, and Po2 on study days 6 and 14. Treatment of metabolic acidosis was permitted at the discretion of the local investigators.
Sample Size and Statistical Methods
It was determined that 50 participants per study group would permit detection of a difference of 1.6 g/kg per day in body weight assuming an SD of 2.8 g/kg per day with α = 0.05 using a 2-tailed test, and a power of 80%. Two statistical analyses were conducted. A primary analysis (or study population analysis) was performed on data from all infants who received HMF, similar to an intent-to-treat analysis. A secondary analysis (per-protocol efficacy analysis) was performed on data from infants who (1) received ≥80% of their energy intake from human milk fortified with study fortifier for at least the first 2 weeks of the study and who were required to have nothing by mouth for no more than 2 days during this period; (2) consumed study fortifier at full strength on study day 3; (3) received no glucocorticoid therapy during the study; and (4) had no disease that affected growth during the period of the study.
Analysis of covariance was used to analyze weight growth rates, including weight on study day 1 as a covariate. Analysis of variance was used to analyze length and head circumference growth rates. The Wilcoxon test was used to compare the Kaplan-Meier survival curves (time to reach full feeding volume) of the study groups. Analysis of variance, Kruskal-Wallis test, and Fisher’s exact test were used where appropriate to analyze other secondary outcomes.
A total of 150 preterm infants were enrolled and randomized at 14 study sites between October 2008 and July 2010, as shown in Fig 1; 106 infants completed the 28-day study. Seventy-two of the 146 participants who received study fortifiers weighed <1 kg at birth. The range of weights for the control and LHMF infants were 530 to 1240 g and 700 to 1250 g, respectively. There were no statistically significant differences in birth characteristics of the infants (Table 2). Use of donor milk was similar between groups (control, 25%; LHMF, 19%; P = .42).
No significant differences were detected in rates of mean ± SE weight gain between the LHMF and control groups for either the primary analysis (LHMF: 15.8 ± 0.5 g/kg per day; control: 15.7 ± 0.5 g/kg per day; P = .8) or in the efficacy analyses (LHMF: 16.6 ± 0.5 g/kg per day; control: 15.8 ± 0.5 g/kg per day; P = .23). However, mean length growth rate (ie, linear growth) was higher for the LHMF group compared with the control group for the primary analysis (0.16 ± 0.006 cm/d vs 0.14 ± 0.006 cm/d; P = .03) and in the efficacy analysis (0.17 ± 0.006 cm/d vs 0.14 ± 0.006 cm/d; P = .012). There were no differences in head circumference growth rate for the primary (LHMF: 0.15 ± 0.004 cm/d; control: 0.14 ± 0.004 cm/d; P = .080) or efficacy analyses (LHMF: 0.16 ± 0.005 cm/d; control: 0.15 ± 0.006 cm/d; P = .43).
Although there were no significant differences in achieved weight, length, or head circumference on day 14 (Table 3), achieved weight and length in the overall study population were significantly higher for infants in the LHMF group compared with the control group on day 28 (P = .038 and P = .010, respectively). In the efficacy analysis, achieved weight, length, and higher head circumference were greater in the LHMF group compared with the control group on day 28 (P = .004, .003, and .043, respectively). Furthermore, ponderal indexes were similar between groups on day 28 for the overall and efficacy analyses (P = .849 and P = .576, respectively).
There was no difference between groups in the time to achieve full feeding volume (enteral intake ≥140 mL/kg) (Fig 2). Daily gastric residuals, incidence of abdominal distention, regurgitation/emesis of milk, feedings withheld ≥4 hours at a time due to intolerance, incidence of bloody stools, and oliguria were also similar. Local physicians added protein fortifiers to the fortified breast milk in 3 infants from each group after study day 14.
Data for laboratory measurements are shown in Table 4. Of note, prealbumin and albumin levels were higher in the LHMF group compared with the control group on day 14 (P = .007 and 0.04, respectively) as was prealbumin on day 28 (P = .029). BUN was higher in the LHMF group at all 3 time points (all P < .05). There were small differences between groups in chloride, CO2, and phosphorus but no differences in serum calcium or alkaline phosphatase. In addition, there were no differences in the proportion of infants who had clinically significant laboratory outcomes on days 14 and 28 (ie, BUN <5 or >30 mg/dL, CO2 <18 or >30 mEq/L, phosphorus <5 or >8 mg/dL, or alkaline phosphatase >500 U/L).
The pH was slightly higher in the control group compared with the LHMF group on day 6 (7.41 ± 0.01 vs 7.37 ± 0.01; P = .004) but not on day 14 (7.40 ± 0.01 vs 7.39 ± 0.01; P = .38). There was no difference between groups for Pco2 on day 6; for day 14, the mean was higher in the control group compared with the LHMF group (43.24 ± 1.01 torr vs 37.29 ± 1.06 torr; P < .001). Means for Hco3 were higher for infants in the control group compared with the LHMF group on day 6 (25.9 ± 0.62 mEq/L vs 22.3 ± 0.69 mEq/L; P < .001) and day 14 (26.6 ± 0.59 mEq/L vs 22.6 ± 0.62 mEq/L; P < .001). These statistically significant differences were not reflected in differences in clinical outcome; that is, similar numbers of infants had a pH <7.3 (day 6: control, n = 7; LHMF, n = 5; day 14: control, n = 3; LHMF, n = 5). Only 1 infant in the LHMF group and 1 infant in the control group were identified by their physician as having acidosis on day 6, and no treatment of acidosis was given to any infant in either group by the managing physicians.
The overall incidence of confirmed sepsis was 12% and confirmed NEC was 3%. No differences were observed between groups for the number of infants with confirmed sepsis (P = .80) or confirmed NEC (P = .367), including those with a birth weight ≤1000 g. The groups were also similar with regard to the number of infants for whom at least 1 serious adverse event was reported (P = 1.000).
Preterm infants fed human breast milk supplemented with a new, ultraconcentrated LHMF that is designed to comply with current recommendations to exclude powder products from the NICU, and to increase the quantity of protein provided to preterm infants, showed improved growth compared with those fed using a conventional powder HMF. Those infants fed breast milk fortified with LHMF had significantly greater linear growth and greater achieved body weight, length, and head circumference on study day 28. The effect of LHMF was even more pronounced for those in the subgroup that more closely adhered to the protocol.
New expert recommendations suggest that preterm infants with birth weights <1 kg receive 4.0 to 4.5 g/kg per day of protein (3.6–4.1 g/100 kcal).16 This recommendation is based on previous studies that showed increased protein accretion with intake of increased protein17–19 and that even a small deficit in protein intake impairs both growth in lean body mass and linear growth.20 Senterre and Rigo have recently shown the efficacy of providing higher protein parenterally during the first weeks of life.21 The current study extends their findings to include enteral protein for infants fed breast milk, providing additional support for these new recommendations, as protein was the major nutritional difference between the 2 fortifiers in our study.
To the best of our knowledge, no previous study has assessed the efficacy or safety of feeding these higher protein intakes to preterm infants. Because of concerns for feeding high amounts of protein to preterm infants, we assessed the metabolic safety of providing an intake of ∼4 g/kg per day of protein. As observed previously by Kashyap et al,20 administration of a higher protein content resulted in significantly greater BUN, but this had no adverse clinical consequences and remained within the normal limits for this population. There is no consensus concerning the safe upper limit of BUN in preterm infants, but it is recognized that lower values may reflect a deficiency of protein intake. Similarly, all other markers of protein status and metabolism were within normal limits for this patient population despite any statistical differences between groups.22 When considered collectively, these findings suggest that the additional protein in the LHMF is being efficiently used to support infant growth and that it is being tolerated metabolically. In fact, it has been suggested that infants given an insufficient amount of protein (as in the control powder), do not grow as well as those give an appropriate amount of protein (as in the LHMF formulation).21
Increasing protein intake may result in metabolic acidosis regardless of the source of nutrition. Although the liquid fortifier is acidic in nature, the regulatory function of the gastrointestinal tract should account for and balance this acidity. We observed small, albeit statistically significant, group differences in mean pH on study day 6 and Hco3 on days 6 and 14. However, these differences are unlikely to be clinically significant because of the following: (1) pH measurements were within the normal physiologic range for this population22,23; (2) the incidence of pH <7.3, the number used by most neonatologists to make a clinical diagnosis of acidosis, was similarly low in the 2 groups; and (3) the number of infants treated for acidosis did not differ between groups. Clinically speaking, the concern with acidosis is the effect on growth; linear growth improved in the group receiving the LHMF, which would not be expected if the alterations in Hco3 were clinically significant because metabolic acidosis can impair linear growth.24,25
A limitation of our study is that we did not know the actual protein content of the breast milks being fed to study participants. However, a strength of our study is the assessment of outcome in infants managed with a variety of breast milks in a “real-life” NICU setting. Given the variability of breast milk protein content,26–30 we estimate that the protein:energy ratio for human milk fortified with LHMF may range from ∼3.2 to 4.0 g/100 kcal (2.1–2.7 g/100 mL). Although using additional protein supplements after study day 14 was permitted, few attending physicians chose to do so. We speculate that the better growth that the higher protein LHMF provides may preclude clinicians from using higher feeding volumes, additional protein supplements, or breast milk formulations concentrated >24 kcal/ounce . NICUs that routinely concentrate milks >24 kcal/ounce may need to assess the nutrient ratios that could result when using this new fortifier.
Current powdered fortifiers only marginally dilute host defense factors in human milk; however, they are not commercially sterile. Liquid products used to fortify human milk, including those made from pasteurized human milk, can dilute host defense factors in human milk by nearly 50% (ie, 1:1 dilution). Moreover, some host defense factors are deactivated in pasteurized donor human milk.31 Although not the primary outcome of this study, the use of ultraconcentrated LHMF did not result in significant differences in adverse events related to host defense properties of human milk, suggesting that the dilution of host defense factors was minimal. This notwithstanding, our study was not powered to detect differences in serious morbidities such as sepsis or NEC.
Feeding a traditional powdered fortifier or the new liquid ultraconcentrated fortifier to preterm infants was safe and well tolerated. When added to breast milk, the new LHMF with higher protein enhances both length as well as weight growth in preterm infants with birth weight ≤1250 g, with minimal metabolic and host defense impact compared with currently available powdered fortifier. Furthermore, it permits avoidance of risks associated with the use of powder formulas in the NICU.
The authors gratefully acknowledge the guidance provided by the data monitoring board: Joseph Garcia-Prats, MD, E. O’Brian Smith, PhD, and William Heird, MD. The authors thank study investigators and their staff for their cooperation: Khalid Awad, MD, William Meetze, MD, Cristina Javier, MD, Mitchell Stern, MD, Bhagya Puppala, MD, Mohammad Alattar, MD, Renu Sharma, MD, Raul Lazarte, MD, Mary Lim, MD, Henry Rozycki, MD, Billy Thomas, MD, Ivan Hand, MD, and Rajan Wadhawan, MD. In addition, Susan Hazels Mitmesser, PhD, is acknowledged for coordination and interpretation of study results and manuscript development; Cheryl Harris, MS, for input in study design, operation of the study, statistical analysis, and interpretation of study results; and Suzanne Stolz for management of the study.
- Accepted May 31, 2012.
- Address correspondence to Carol Lynn Berseth, MD, Mead Johnson Nutrition, 2400 W. Lloyd Expressway, Evansville, IN 47721. E-mail:
This study was sponsored by Mead Johnson Nutrition. All authors have made substantive intellectual contributions to the concept, design, analysis, and interpretation of data. All authors have contributed, revised, and agree with the contents of the manuscript.
FINANCIAL DISCLOSURE: Drs Berseth and Walsh are employees of Mead Johnson Nutrition. Drs Moya and Sisk’s institutions were provided funding to defray the costs of enrolling and monitoring infants during the study. Dr Moya was provided travel funds to present some of the data at the International Conference on Nutrition and Growth.
FUNDING: This study was supported by funding from Mead Johnson Nutrition.
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- Copyright © 2012 by the American Academy of Pediatrics