Feeding preterm infants with formula rather than donor breast milk is associated with faster rates of short-term growth, but increased risk of developing necrotising enterocolitis

Karen Tosh*

*Corresponding author for this work

Research output: Contribution to journalComment/debatepeer-review

1 Citation (Scopus)
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Implications for practice and research
Formula milk offers short-term benefits but may not result in any long-term benefits for growth or development over donor breast milk.

Formula milk appears to significantly increase risk of necrotising enterocolitis.

Further methodologically rigorous randomised controlled trials are required to support early enteral feeding strategies.

Artificial formulas and donor breast milk are used as supplements or alternatives for enteral feeding of preterm and low birthweight (LBW) infants when maternal breast milk is insufficient or unavailable. Formula milk offers a degree of certainty in nutritional delivery for infant growth and development; donor breast milk confers less certainty but provides other non-nutritive benefits.1 Effective strategies for early enteral feeding may help mitigate infective and inflammatory sequelae of conditions such as necrotising enterocolitis (NEC). To determine the relative benefits and risks of these alternatives, Quigley and colleagues2 reviewed trials comparing the effects of feeding with formula or donor breast milk on preterm and LBW infants’ growth and development.

This systematic review considered randomised or quasirandomised controlled trials which included preterm (<37 weeks) or LBW infants. The interventions included infants who were enterally fed standard or preterm (nutrient-enriched) formulas versus donor breast milk, either entirely or to supplement maternal breast milk. Primary outcome measures included weight gain, head and linear growth and neurodevelopmental outcomes using validated assessment tools. Secondary outcomes included all-cause mortality and specific incidence of NEC. The study employed standard Cochrane neonatal search strategies to review CINAHL and OVID databases MEDLINE, Embase and Maternity and Infant Care Database. Two reviewers screened the literature to identify eligible studies for data extraction and assessment of quality, risk of bias and heterogeneity. Eleven studies were identified from Europe and North America with a total of 1809 participants. Qualitative and quantitative synthesis (meta-analysis) was undertaken using a fixed effects model. Five other studies were still ongoing and another was waiting for assessment and translation, so were not included.

A challenge for this review was the methodological quality of the studies, which was variable. Selection, performance/detection and reporting biases in particular were identified as unclear or high risk for some studies. Certainty of the evidence (Grading of Recommendations Assessment, Development and Evaluation) was downgraded to medium on the basis of heterogeneity for growth outcomes and imprecision for neurodevelopmental, all-cause mortality and NEC outcomes. While formula-fed infants had higher in-hospital weight gain this effect did not translate to long-term growth. There was no evidence of effect on neurodevelopmental outcomes. There was also no effect on all-cause mortality, but there was significant increase in risk of NEC associated with formula feeding.

This study examined the relative risks and benefits of using formula versus donor breast milk for enteral feeding of infants where availability of maternal breast milk is insufficient. The need for an evidence-based approach to early feeding strategies is apparent and the issues of methodological quality around bias and heterogeneity in the available literature are disappointing. It is encouraging that there are a number of studies currently investigating this question especially given that 7 of the 11 studies here are over 30 years old.

The review is important in terms of identifying best practice in neonatal care, but quality issues aside it is difficult to assess the effects when different types of formula are used and both maternal and donor breast milk may or may not be fortified with additional nutrients. Indeed fortification is now a fairly common approach3 not reflected in some of the older studies here. This study also helps to contribute to discussions about the goals of feeding which may not just be about adequate nutrition alone. Parental choice, promotion of breast milk and by extension breast feeding and avoidance of unintended consequences are important considerations. The increased incidence of NEC associated with formula negatively impacts length of hospital stay,4 the experience of parents and not least causes suffering to the infant. While clinicians may find certainty of nutritional delivery reassuring for short-term growth until there is greater clarity about the risks and the benefits, careful consideration should continue to be given when deciding what enteral feed alternatives to offer preterm and LBW infants.
Original languageEnglish
Article number18
JournalEvidence-Based Nursing
Issue number1
Early online date12 Oct 2018
Publication statusPublished - 17 Dec 2018
Externally publishedYes


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