MANUSCRIPT CITATION:

Ford SL, Lohmann P, Preidis GA, Gordon PS, O’Donnell A, Hagan J, Venkatachalam A, Balderas M, Luna RA, Hair AB. Improved feeding tolerance and growth are linked to increased gut microbial community diversity in very-low-birth-weight infants fed mother’s own milk compared with donor breast milk. Am J Clin Nutr. 2019 Apr 1;109(4):1088-1097. doi: 10.1093/ajcn/nqz006. PMID: 30982856

REVIEWED BY:

Nikolina Zdraveska
Assistant Professor of Pediatrics
Deparment for Neonatology, University Children Hospital Skopje, Macdeonia

TYPE OF INVESTIGATION:  

Prevention, treatment

QUESTION

(P) In a cohort of very low birth weight (VLBW) infants (I) does the feeding with mothers own milk (C) in comparison with donor milk (O) provides increased intestinal microbiota diversity and a greater weight gain (T) from birth until 36 week postmenstrual age?   

METHODS

• Design: prospective, observational
• Allocation: N/A – because of the well known benefits of mothers own milk (MOM) to VLBW infants randomization is not ethically acceptable
• Blinding: N/A
• Follow-up period: Up to 36 weeks post menstrual age (PMA) or until discharge
• Setting: a single center NICU at Texas Children Hospital –Pavilion for Women, affiliated with Baylor College of Medicine, Houston, Texas, USA
• Patients: All premature infants with a birth weight <1500g admitted to NICU at within the first 72 h of life
  • Inclusion criteria
    • Infants aged < 72 hours, birth weight <1500 g birth without barriers for enteral milk feeding (mother’s own milk and/or donor milk)
  • Exclusion criteria
    • Anomalies or birth defects that preclude enteral feeding (eg. gastroschisis), severe perinatal hypoxia or <50% projected survival based on the National Institute of Child Health and Human Development Neonatal Research Network Extremely Preterm Birth Outcome Data Calculator 
• Intervention: All infants included in the study were started on parenteral nutrition with gradually increasing the enteral feeds according to hospital standardized feeding protocols for infants <1250g and 1250 – 1500g birth weight. By reviewing the milk bank preparation sheets for each enrolled infant with a precise specification of milliliters milk volume, grouping was made in the following cohorts: 1) Mother’s own milk (MOM) cohort – infants fed >50% with mother’s own milk; 2) Donor milk (DM) cohort – infants who received <50% mother’s milk.       
• Outcomes:
  • Primary outcome:
    • Diversity of the intestinal microbiota: Stool samples collected during the first 6 weeks of life were analyzed for microbial diversity and compared between mothers own milk (MOM) and donor milk (DM) cohorts
    • Growth velocities (weight, length, head circumference) measured weekly and expressed as g/kg/day; cm/week and cm/week, respectively from birth to 36-week PMA
  • Secondary outcomes:
    • Feeding tolerance: Assessed by multiple factors: 1) number of days required to reach full enteral feeding volumes of 140-160 ml/kg/day, 2) number of feeds per total days during the study period, 3) days with no enteral feeds after feeding initiation and 4) days with total parenteral nutrition
    • Rates of serious neonatal morbidities such as:
      • Necrotizing enterocolitis – defined as Stage IIA NEC per Modified Bell’s Staging Criteria
      • Spontaneous intestinal perforation – defined as intestinal free air on radiograph, or visualized directly via laparotomy
      • Late onset sepsis – defined with positive blood culture after 72h of age
      • Bronchopulmonary dysplasia – defined as need for supplemental oxygen >21% for >28 days; severe BPD oxygen >30% or positive pressure ventilation at 36wk PMA.
• Sample Size: The sample size was determined based on a primary endpoint of weight gain from birth to 36wk postmenstrual age, with an enrollment goal of 125 infants in order to achieve adequate sample size.
• Analysis: The stool samples were analyzed via 16S rRNA sequencing to determine the diversity of intestinal microbiota. Organisms classification to species were based on an individual operational taxonomic units (OTUs) level of significance. Bacterial diversity, richness and relative abundance to the OTUs were evaluated using QIIME.
• Statistical considerations: The clinical outcomes between the groups were compared using the following tests: Wilcoxson’s rank sum test and Fisher’s exact test for bivariate analysis and  multivariable linear and logistic regression analysis using SAS version 9.4 (SAS Institute Inc.). 

MAIN RESULTS

Out of 125 enrolled infants, 117 completed the study and were distributed as follows: MOM cohort (n=74), receiving on average 91.2% mother’s milk and DM cohort (n=43), receiving only 14.3% mother’s milk vs. 85.7% donor milk. Adequate stools samples for analysis were collected from 90 infants. There were no differences in the baseline demographic characteristics, as well as surfactant administration, early empiric antibiotics or antibiotic treatment within the first 14 days between the groups except for higher prophylactic usage of indomethacine in the DM group.   

• Microbiota analysis results: MOM infants demonstrated significantly higher diversity in terms of OTUs richness compared to the DM infants (p=0.013). Diversities among microbial communities between MOM and DM group over time were as follows:
  • Phylum level:
    • No significant difference between the groups during the first 2 weeks of life
    • Significantly higher abundance of Actinobacteria (p=0.032) and decreased abundance of Firmicutes (p=0.011) in MOM cohort compared to DM cohort by week 4
  • Genus level:
    • Significantly increased abundance of Bifidobacterium (p=0.026), Bacteroides (p=0.046) and Enterococcus (p<0.01) in MOM cohort in comparison to DM cohort by 4-6th week of life
    • Significantly higher abundance of Staphylococcus in DM infants group (p=0.014)
• Additional comparisons were made between the groups in terms of other variables that may influence the microbiota development, such as mode of delivery and antibiotic exposure.
  • No significant difference in gut microbiota was observed in both MOM and DM cohort between infants delivered via cesarean section or vaginally (small sample size for vaginal delivery infants and high rates of cesarean delivery observed in both groups: MOM: 82% and DM: 88%).
  • MOM infants had higher genera abundance after the antibiotic exposure in comparison with DM infants during the second week of life

• Clinical outcome results: MOM infants exhibited better growth parameters (weight, length, head circumference, growth velocity) and improved feeding tolerance compared to the DM infants (Table 1). Also, cumulatively severe morbidities (NEC, spontaneous intestinal perforation, sepsis, severe BPD or death) were more prevalent in the DM group.

Table 1. Significant differences in clinical outcomes of the study groups.

CONCLUSION

The results of the study showed that MOM-fed infants have increased intestinal microbial diversity at phylum and genius level by 4^th and 6^th postnatal week, as well as better feeding tolerance and superior growth compared to DM-fed infants from birth to 36w PMA.

COMMENTARY

Early infant nutrition plays a crucial role in shaping future health (1) and human milk is the first choice for all infants. It has numerous benefits, including improved neurological, immunological or metabolic outcomes, and makes a significant contribution to early intestinal microbiome development (2-4). Mother’s own milk is even more important for preterm infants, as they frequently have a different gut microbiota to term infants, with reduced species diversity. This makes them more vulnerable to serious intestinal inflammatory conditions like necrotising enterocolitis (5,6). Numerous studies have demonstrated the benefits of feeding human milk, rather than formula, in intensive care units, but there has been a lack of studies comparing maternal and donor milk (7,8). 

The Ford et al study was the first to compare the development of intestinal microbiota and clinical outcomes in infants with an exclusive human milk diet of mother’s own milk or donor milk. They enrolled 125 infants born weighing less than 1500g, without barriers for enteral feeding, and grouped them based on which milk accounted for more than 50% of their diet.   

Their results highlight several points. First,  infants fed mother’s own milk or donor milk had significantly different microbiota at the phylum and genius level by four and six weeks of life. Those fed with mother’s own milk had increased microbial diversity and an abundance of beneficial bacteria, such as Bifidobacterium (p=0.02) and Bacteroides (p=0.04) that protect against severe morbidities. Second, they were 60% less likely to experience feeding intolerance than those who received donor milk, leading to improved growth parameters. This was consistent with previously studies that suggested possible explanations, such as lower protein content in donor milk or diminished lipase activity due to pasteurisation. (3,9) Third, mother’s own milk consistently protected the gut microbiota from the effect of antibiotics, which may have important clinical implications.

The study strengths were the large sample size, longitudinal design and multiple microbiota assessments, while the limitations were its observational design and the inability to account for confounding variables and other potential sources of bias.

The study adds additional data to the benefits of mother’s own milk for very low birth weight infants and further supports efforts to improve lactation in neonatal care units and maintain the mother’s milk supply during extended hospital stays.

However, further research is needed on the beneficial effects of probiotics, adjusted by feeding type, on microbiological and clinical outcomes.  It is plausible that nutrition and probiotic supplementation may act together in the preterm infant’s gut, leading to a global improvement in neonatal health.

REFERENCES

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6. Warner BB, Deych E, Zhou Y, Hall-Moore C, Weinstock GM, Sodergren E, Shaikh N, Hoffmann JA et al.Gut bacteria dysbiosis and necrotising enterocolitis in very low birthweight infants: a prospective case-control study. Lancet. 2016; 387(10031):1928-36.
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