Early fortification of human milk versus late fortification to promote growth in preterm infants

Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the effect of early fortification of human milk versus late fortification on growth and incidence of NEC in preterm infants; and to assess whether the effect varies based upon gestational age, birth weight, or type of fortifier (bovine‐milk‐based HMF or human‐milk‐based HMF or formula powder fortification).

Background

Description of the condition

Preterm birth places the infant at high risk of nutritional deprivation and results in interruption of growth. It is a challenge to sustain in‐utero growth velocity after birth in preterm infants due to the difficulty in maintaining adequate protein‒energy supplementation and due to the catabolic state of infants secondary to postnatal illnesses such as sepsis, necrotising enterocolitis (NEC), chronic lung disease, need for assisted ventilation and exposure to postnatal steroids (Lima 2014).

Extremely low birth weight (ELBW) infants take as long as 16 days to regain birth weight (Steward 2002). The rate of extra‐uterine growth restriction (EUGR) at discharge is unacceptably high, ranging from 23% in infants born at 34 weeks' gestation to 71% in those born at 23 weeks' gestation (Clark 2003). Moreover, being small for gestational age (SGA) at birth increases the likelihood of EUGR at discharge by six times (Freitas 2016). The growth failure continues even after discharge. Data from the National Institute of Child Health and Human Development (NICHD) cohort in the USA showed that 40% of ELBW‐SGA infants had weight, length and head circumference less than the 10th percentile at 18 to 22 months' corrected age (Dusick 2003). Growth restriction in early infancy has long‐term consequences in the form of stunting, neurodevelopmental impairment and early onset of adult diseases such as hypertension, diabetes, obesity and hypercholesterolaemia (Barker 1989; Cooke 2004; Lucas 1994; Lucas 2004).

Early aggressive nutrition is the norm in the management of preterm infants. Nutritional requirement in the initial few days of life are usually met by total parenteral nutrition (TPN), which is started from day one of life and continued until adequate enteral feeds are established. However, TPN administration is technically demanding (need for trained staff, laminar flow, laboratory backup and appropriate equipment) and it is expensive. It may cause adverse effects such as azotaemia, metabolic acidosis, hyperlipidaemia, cholestasis and catheter‐related complications (Calkins 2014). Moreover, each day without enteral nutrition increases the likelihood of EUGR by 8% (Freitas 2016). Hence, enteral feeds should be started early and full enteral feeds should be achieved as soon as possible.

Description of the intervention

Human milk is the best enteral food for preterm infants. However, unfortified human milk does not provide a sufficient quantity of protein to support growth and lean body mass accretion in very low birth weight infants (Morales 2007). The amount of calcium and phosphorus provided by unfortified human milk is also too low to match in‐utero accretion rate (Boyd 2007; Lucas 1996). The most common method used to increase enteral supplementation of calories, protein and minerals is by adding multi‐component human milk fortifier (HMF) to human milk. On average, while unfortified human milk provides 67 Kcal and 1.1 g of protein per 100 mL, human milk with HMF provides 80 Kcal and 2 g of protein per 100 mL. A recent Cochrane meta‐analysis showed that fortification of human milk with a multi‐component HMF improved in‐hospital growth rates; there was no significant difference, however, in other major clinical outcomes (Brown 2016).

There is no definite guideline on when to start HMF. The common practice is to start fortification when the enteral feed volume reaches around 100 mL/kg/day (Berseth 2004; Gathwala 2007; Mukhopadhyay 2007). The delay in fortification is because of clinicians’ concern about the risk of NEC and feed intolerance. There is some evidence, however, to show that HMF fortification may be started as early as the first enteral feed (Alizadeh 2017; Maas 2013; Mimouni 2017; Shah 2016; Sullivan 2010; Tillman 2012).

How the intervention might work

Early fortification of human milk would improve the protein‒calorie and mineral intake in preterm infants (Shah 2016; Tillman 2012). This may avoid the dip in nutrition and improve the time taken to regain birth weight. This may also improve further postnatal growth and decrease the risk of EUGR (Steward 2002). Early fortification may be especially important for infants who receive pasteurised donor milk, which contains lower levels of protein, energy and minerals than own mother’s expressed breast milk (Arslanoglu 2010).

On the other hand, since most of the available HMFs are based on cow's milk and since HMF increases the osmolarity of feeds, early fortification may increase the risk of feed intolerance and NEC. This may result in interruption of feeds and delay in reaching full enteral feeds, which in turn increases the duration of TPN and parenteral‐nutrition‐associated liver disease (Calkins 2014). It may also increase the number of days of central venous line (CVL) usage, thus increasing the risk of late‐onset sepsis and other CVL‐related complications (Hermansen 2005).

Why it is important to do this review

Given the potential use of early fortification of human milk in improving postnatal growth, as well as the possible risks, we will undertake a systematic review that identifies and appraises data from randomised controlled trials, to provide a synthesis of evidence to inform practice and research. We have not found any existing systematic review on this topic.

Objectives

To assess the effect of early fortification of human milk versus late fortification on growth and incidence of NEC in preterm infants; and to assess whether the effect varies based upon gestational age, birth weight, or type of fortifier (bovine‐milk‐based HMF or human‐milk‐based HMF or formula powder fortification).

Methods

Criteria for considering studies for this review

Types of studies

Randomised or quasi‐randomised trials and cluster‐randomised trials will be eligible for inclusion in the review.

Types of participants

Preterm infants (< 37 weeks' gestation).

Types of interventions

Intervention: early fortification of human milk, started at an enteral feed volume of less than 100 ml/kg/day or less than 7 days of postnatal age.

Comparison: late fortification, started at an enteral feed volume of 100 ml/kg/day (or more) or 7 days (or more) of postnatal age.

The fortification should be done with a multi‐component fortifier containing carbohydrate, protein, lipid and micro‐nutrients, which could be a bovine‐milk‐based HMF, human‐milk‐based HMF or formula powder.

Types of outcome measures

Primary outcomes

1. Time to regain birth weight (days) and subsequent rate of weight gain (g/kg/day), linear growth (cm/week) and increase in head circumference (cm/week) during the initial hospitalisation period.

2. Incidence of necrotising enterocolitis (NEC) stage 2 or 3 (Modified Bell’s staging, Walsh 1986).

Secondary outcomes

1. Incidence of surgical NEC.

2. Time to reach full enteral feeds ≥ 150 mL/kg/day.

3. Incidence of extra‐uterine growth restriction at discharge (number of infants with weight < 10th percentile for the index population).

4. Proportion of infants with ≥ 1 episode of feed interruption lasting ≥ 12 hours.

5. Duration of total parenteral nutrition (TPN) (days).

6. Incidence of parenteral‐nutrition‐associated liver disease.

7. Duration of central venous line (CVL) usage (days).

8. Incidence of invasive infection as determined by culture of bacteria or fungus from blood, cerebrospinal fluid, urine, or from a normally sterile body space.

9. All‐cause mortality before discharge or up to 44 weeks’ postmenstrual age.

10. Duration of hospital stay (days).

11. Growth measures following discharge from hospital to latest follow‐up (weight, length and head circumference).

12. Neurodevelopmental outcomes assessed after 12 months' corrected age: neurological evaluations; developmental scores; and classifications of disability, including auditory and visual disability. We will define neurodevelopmental impairment as the presence of 1 or more of the following: non‐ambulant cerebral palsy; developmental quotient more than 2 standard deviations below the population mean; and blindness (visual acuity less than 6/60) or deafness (any hearing impairment requiring — or unimproved by — amplification).

Search methods for identification of studies

We will use the criteria and standard methods of Cochrane and Cochrane Neonatal (see the Cochrane Neonatal search strategy for specialized register). We will search for errata or retractions from included studies published in full text on PubMed (www.ncbi.nlm.nih.gov/pubmed) and report the date this was done within the review.

Electronic searches

We will conduct a comprehensive search including: Cochrane Central Register of Controlled Trials (CENTRAL, current issue) in the Cochrane Library; MEDLINE via Ovid (1946 to present); PubMed (1966 to present); Embase via Ovid (1974 to present); and CINAHL via EBSCOhost (1981 to present). We will use Cochrane Neonatal's search strategy for neonates and randomised controlled trials (see Appendix 1) in combination with terms for fortification of human milk. The full MEDLINE search strategy is available in Appendix 1 and we will adapt it to suit the other databases. We will not apply language restrictions.

We will search clinical trials registries (ClinicalTrials.gov; the World Health Organization’s International Clinical Trials Registry Platform; and the ISRCTN Registry) for recently completed or ongoing trials.

Searching other resources

We will also search the reference lists of any articles selected for inclusion in this review in order to identify additional relevant articles. We will search the proceedings of the annual meetings of the Paediatric Academic Societies (1993 to present), the European Society for Paediatric Research (1995 to present), the Royal College of Paediatrics and Child Health (2000 to present), and the Perinatal Society of Australia and New Zealand (2000 to present). Trials reported only as abstracts will be eligible if sufficient information is available from the report, or from contact with the authors, to fulfil the inclusion criteria.

Data collection and analysis

We will use the standard methods of Cochrane Neonatal and Cochrane (Higgins 2011).

Selection of studies

Two review authors (TA and ST) will screen the title and abstract of all studies identified by the search strategy and independently will assess the full‐text articles for all potentially relevant trials. We will exclude the studies that do not meet all of the inclusion criteria and we will state the reason for exclusion. We will discuss any disagreements until consensus is achieved.

We will record the selection process in sufficient detail to complete a 'Characteristics of excluded studies' table and a PRISMA flow diagram (Moher 2009).

Data extraction and management

Two review authors (TA and ST) will extract data independently using a data collection form to aid extraction of information on design, methodology, participants, interventions, outcomes and treatment effects from each included study. We will discuss any disagreements until we reach a consensus. If data from the trial reports are insufficient, we will contact the trialists for further information.

Assessment of risk of bias in included studies

Two review authors (TA and ST) independently will assess the risk of bias (low, high, or unclear) of all included trials using the Cochrane ‘Risk of bias’ tool, as described in Higgins 2011, for the following domains.

1. Sequence generation (selection bias)

2. Allocation concealment (selection bias)

3. Blinding of participants and personnel (performance bias)

4. Blinding of outcome assessment (detection bias)

5. Incomplete outcome data (attrition bias)

6. Selective reporting (reporting bias)

7. Any other bias

We will discuss any disagreements until we reach a consensus. See Appendix 2 for a more detailed description of risk of bias for each domain.

Measures of treatment effect

We will analyse the treatment effects in the individual trials using Review Manager 2014 and report risk ratio (RR) and risk difference (RD) for dichotomous data and mean difference (MD) for continuous data, with respective 95% confidence intervals (CIs). We will determine the number needed to treat for an additional beneficial outcome (NNTB) or an additional harmful outcome (NNTH) for analyses with a statistically significant difference in the RD.

Unit of analysis issues

The unit of analysis will be the participating infant in individually randomised trials. For cluster‐randomised trials, we will undertake analysis at the level of the individual while accounting for the clustering in the data using an estimate of the intra‐cluster correlation coefficient (ICC) derived from the trial (if possible), or from another source (Higgins 2011). If ICCs from other sources are used, we plan to report this and conduct sensitivity analyses to investigate the effect of variation in the ICC. If we identify both cluster‐randomised trials and individually randomised trials, we will synthesise the relevant information. We plan to combine the results where there is little heterogeneity between study designs, and we consider interactions between the effects of the intervention and the choice of randomisation unit to be unlikely.

Dealing with missing data

We will request additional data from the trialists if data on outcomes are missing or reported unclearly. Where data are still missing, we will examine the impact on effect size estimates in sensitivity analyses using the 'best‒worst case scenario' technique.

Assessment of heterogeneity

We will examine the treatment effects of individual trials and heterogeneity between trial results by inspecting the forest plots. We will calculate the I² statistic for each RR analysis to quantify inconsistency across studies and describe the percentage of variability in effect estimates that might be due to heterogeneity rather than to sampling error. Heterogeneity will be classified as none (< 25%); low (25% to 49%); moderate (50% to 74%); or high (≥ 75%). If we detect moderate or high heterogeneity (I² ≥ 50%), we will explore the possible causes (for example, differences in study design, participants, interventions, or completeness of outcome assessments).

Assessment of reporting biases

If 10 or more trials are included in a meta‐analysis, we will examine a funnel plot for asymmetry.

Data synthesis

We will analyse all infants randomised on an intention‐to‐treat basis and treatment effects in the individual trials using a fixed‐effect model to combine the data. For meta‐analyses of categorical outcomes we will calculate typical estimates of RR and RD, each with 95% CIs; for continuous outcomes we will calculate the mean difference (MD) if outcomes are measured in the same way between trials, and standardised mean difference (SMD) to combine trials measuring the same outcome using different scales. We will determine the number needed to treat for an additional beneficial outcome (NNTB) or an additional harmful outcome (NNTH) for analyses with a statistically significant difference in the RD. Where meta‐analysis is judged to be inappropriate, we will analyse and interpret individual trials separately.

Quality of evidence

We will use the GRADE approach, as outlined in the GRADE Handbook, to assess the quality of evidence for the main comparison at the outcome level (Schünemann 2013).

Two review authors (TA and ST) will independently assess the quality of the evidence for outcomes identified as critical or important for decision making. We will consider evidence from randomised controlled trials as high quality but downgrade the evidence one level for serious (or two levels for very serious) limitations based upon the following: design (risk of bias); consistency across studies; directness of the evidence; precision of estimates; and presence of publication bias. We will use the GRADEpro GDT (Guideline Development Tool) to create a ‘Summary of findings’ table to report the quality of the evidence.

The GRADE approach results in an assessment of the quality of a body of evidence in one of four grades.

1. High: we are very confident that the true effect lies close to that of the estimate of the effect.

2. Moderate: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.

3. Low: our confidence in the effect estimate is limited — the true effect may be substantially different from the estimate of the effect.

4. Very low: we have very little confidence in the effect estimate — the true effect is likely to be substantially different from the estimate of effect.

Subgroup analysis and investigation of heterogeneity

1. Based on gestational age: ≤ 27 weeks' gestation; 28 weeks' gestation to 31 weeks' gestation; ≥ 32 weeks' gestation

2. Based on birth weight: < 1000 grams; 1000 grams to 1499 grams; ≥ 1500 grams

3. Small for gestational age versus appropriate for gestational age infants (classified using birth weight relative to the reference population)

4. Type of HMF (bovine‐milk‐based HMF, human‐milk‐based HMF, formula powder)

Sensitivity analysis

We will undertake sensitivity analyses to determine if the findings are affected by including only studies of adequate methodology (low risk of bias), defined as adequate randomisation and allocation concealment, blinding of intervention and measurement, and less than 10% loss to follow‐up.

Appendices

Appendix 1. Cochrane Neonatal search strategy

MEDLINE via Ovid:

1. exp infant, newborn/

2. (newborn* or new born or new borns or newly born or baby* or babies or premature or prematurity or preterm or pre term or low birth weight or low birthweight or VLBW or LBW or infant or infants or infantile or infancy or neonat*).ti,ab.

3. 1 or 2

4. randomised controlled trial.pt.

5. controlled clinical trial.pt.

6. randomized.ab.

7. placebo.ab.

8. drug therapy.fs.

9. randomly.ab.

10. trial.ab.

11. groups.ab.

12. or/4‐11

13. exp animals/ not humans.sh.

14. 12 not 13

15. 3 and 14

PubMed:

((infant, newborn[MeSH] OR newborn*[TIAB] OR "new born"[TIAB] OR "new borns"[TIAB] OR "newly born"[TIAB] OR baby*[TIAB] OR babies[TIAB] OR premature[TIAB] OR prematurity[TIAB] OR preterm[TIAB] OR "pre term"[TIAB] OR “low birth weight”[TIAB] OR "low birthweight"[TIAB] OR VLBW[TIAB] OR LBW[TIAB] OR infant[TIAB] OR infants[TIAB] OR infantile[TIAB] OR infancy[TIAB] OR neonat*[TIAB]) AND (randomised controlled trial[pt] OR controlled clinical trial[pt] OR randomised[tiab] OR placebo[tiab] OR drug therapy[sh] OR randomly[tiab] OR trial[tiab] OR groups[tiab]) NOT (animals[mh] NOT humans[mh]))

Embase via Ovid:

1. exp prematurity/

2. exp infant/

3. (newborn* or new born or new borns or newly born or baby* or babies or premature or prematurity or preterm or pre term or low birth weight or low birthweight or VLBW or LBW or infant or infants or infantile or infancy or neonat*).ti,ab.

4. 1 or 2 or 3

5. (human not animal).mp.

6. (randomised controlled trial or controlled clinical trial or randomised or placebo or clinical trials as topic or randomly or trial or clinical trial).mp.

7. 4 and 5 and 6

CINAHL:

(infant or infants or infantile or infancy or newborn* or "new born" or "new borns" or "newly born" or neonat* or baby* or babies or premature or prematures or prematurity or preterm or preterms or "pre term" or premies or "low birth weight" or "low birthweight" or VLBW or LBW) AND (randomised controlled trial OR controlled clinical trial OR randomised OR placebo OR clinical trials as topic OR randomly OR trial OR PT clinical trial)

Cochrane Library:

(infant or infants or infantile or infancy or newborn* or "new born" or "new borns" or "newly born" or neonat* or baby* or babies or premature or prematures or prematurity or preterm or preterms or "pre term" or premies or "low birth weight" or "low birthweight" or VLBW or LBW or ELBW or NICU)

MEDLINE search strategy for this protocol:

1. exp Milk, Human/

2. exp Food, Fortified/

3. exp Dietary Supplements/

4. 2 or 3

5. 1 and 4

6. (fortif* adj4 ((human or breast or expressed) adj2 milk*)).mp.

7. (fortif* adj4 ((mother* or maternal or donor*) adj2 milk*)).mp.

8. (supplement* adj4 ((human or breast or expressed) adj2 milk*)).mp.

9. (supplement* adj4 ((mother* or maternal or donor*) adj2 milk*)).mp.

10. (enrich* adj4 ((human or breast or expressed) adj2 milk*)).mp.

11. (enrich* adj4 ((mother* or maternal or donor*) adj2 milk*)).mp.

12. ((fortif* or supplement* or enrich*) adj4 DHM).mp.

13. ((fortif* or supplement* or enrich*) adj4 HM).mp.

14. ((fortif* or supplement* or enrich*) adj4 breastmilk*).mp.

15. 6 or 7 or 8 or 9 or 10 or 11 or 12 or 13 or 14

16. 5 or 15

17. exp infant, newborn/

18. (newborn* or new born or new borns or newly born or baby* or babies or premature or prematurity or preterm or pre term or low birth weight or low birthweight or VLBW or LBW or infant or infants or infantile or infancy or neonat*).ti,ab.

19. 17 or 18

20. randomised controlled trial.pt.

21. controlled clinical trial.pt.

22. randomized.ab.

23. placebo.ab.

24. drug therapy.fs.

25. randomly.ab.

26. trial.ab.

27. groups.ab.

28. or/20‐27

29. exp animals/ not humans.sh.

30. 28 not 29

31. 19 and 30

32. 16 and 31

Appendix 2. 'Risk of bias' tool

We will use the standard methods of Cochrane and Cochrane Neonatal to assess the methodological quality of the trials. For each trial, we will seek information regarding the method of randomisation, blinding and reporting of all outcomes of all the infants enrolled in the trial. We will assess each criterion as being at a low, high, or unclear risk of bias. Both review authors will separately assess each study. We will resolve any disagreement by discussion. We will add this information to the table ‘Characteristics of included studies’. We will evaluate the following issues and enter the findings into the ‘Risk of bias’ table.

1. Sequence generation (checking for possible selection bias). Was the allocation sequence adequately generated?

For each included study, we will categorise the method used to generate the allocation sequence as:

• low risk (any truly random process e.g. random number table; computer random number generator);

• high risk (any non‐random process e.g. odd or even date of birth; hospital or clinic record number); or

• unclear risk.

2. Allocation concealment (checking for possible selection bias). Was allocation adequately concealed?

For each included study, we will categorise the method used to conceal the allocation sequence as:

• low risk (e.g. telephone or central randomisation; consecutively numbered sealed opaque envelopes);

• high risk (open random allocation; unsealed or non‐opaque envelopes, alternation; date of birth); or

• unclear risk

3. Blinding of participants and personnel (checking for possible performance bias). Was knowledge of the allocated intervention adequately prevented during the study?

For each included study, we will categorise the methods used to blind study participants and personnel from knowledge of which intervention a participant received. Blinding will be assessed separately for different outcomes or class of outcomes. We will categorise the methods as:

• low risk, high risk or unclear risk for participants; and

• low risk, high risk or unclear risk for personnel.

4. Blinding of outcome assessment (checking for possible detection bias). Was knowledge of the allocated intervention adequately prevented at the time of outcome assessment?

For each included study, we will categorise the methods used to blind outcome assessment. Blinding will be assessed separately for different outcomes or class of outcomes. We will categorise the methods as:

• low risk for outcome assessors;

• high risk for outcome assessors; or

• unclear risk for outcome assessors.

5. Incomplete outcome data (checking for possible attrition bias through withdrawals, dropouts, protocol deviations). Were incomplete outcome data adequately addressed?

For each included study and for each outcome, we will describe the completeness of data including attrition and exclusions from the analysis. We will note whether attrition and exclusions were reported, the numbers included in the analysis at each stage (compared with the total randomised participants), reasons for attrition or exclusion where reported, and whether missing data were balanced across groups or were related to outcomes. Where sufficient information is reported or supplied by the trial authors, we will re‐include missing data in the analyses. We will categorise the methods as:

• low risk (< 20% missing data);

• high risk (≥ 20% missing data); or

• unclear risk.

6. Selective reporting bias. Are reports of the study free of suggestion of selective outcome reporting?

For each included study, we will describe how we investigated the possibility of selective outcome reporting bias and what we found. For studies in which study protocols were published in advance, we will compare prespecified outcomes versus outcomes eventually reported in the published results. If the study protocol was not published in advance, we will contact study authors to gain access to the study protocol. We will assess the methods as:

• low risk (where it is clear that all of the study’s prespecified outcomes and all expected outcomes of interest to the review have been reported);

• high risk (where not all the study’s prespecified outcomes have been reported; one or more reported primary outcomes were not prespecified outcomes of interest and are reported incompletely and so cannot be used; study fails to include results of a key outcome that would have been expected to have been reported); or

• unclear risk.

7. Other sources of bias. Was the study apparently free of other problems that could put it at a high risk of bias?

For each included study, we will describe any important concerns we had about other possible sources of bias (for example, whether there was a potential source of bias related to the specific study design or whether the trial was stopped early due to some data‐dependent process). We will assess whether each study was free of other problems that could put it at risk of bias as:

• low risk;

• high risk;

• unclear risk.

If needed, we plan to explore the impact of the level of bias through undertaking sensitivity analyses.

Contributions of authors

Both review authors contributed to the development of this protocol.

Sources of support

Internal sources

• Jawaharlal Institute of Postgraduate Medical Education and Research (JIPMER), Puducherry, India.

• Sri Ramachandra Institute of Higher Education and Research (SRIHER), Chennai, India.

External sources

• National Institute of Health Research, UK.

  Editorial support for Cochrane Neonatal has been funded with funds from a UK National Institute of Health Research (NIHR) Cochrane Programme Grant (16/114/03). The views expressed in this publication are those of the authors and not necessarily those of the National Health Service, the NIHR or the UK Department of Health.

• Vermont Oxford Network, USA.

  Cochrane Neonatal Reviews are produced with support from Vermont Oxford Network, a worldwide collaboration of health professionals dedicated to providing evidence‐based care of the highest quality for newborn infants and their families.

Declarations of interest

ST has no conflict of interest to declare.

TA has no conflict of interest to declare.

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