Armanian 2014.

Methods	Quasi‐randomized controlled trial, single centre
Participants	Inclusion criteria: infants with birth weight ≤ 1500 grams, gestational age ≤ 34 weeks, who had no formula feeds. Infants were included when their milk feeding volume reached 30 mL/kg/d. Exclusion criteria: infants with asphyxia, major congenital anomalies, congenital cyanotic heart disease, gastrointestinal system anomalies, proven sepsis, or infection immediately before the start of the study, transferred to other departments, refused to participate Setting: NICUs of the Isfahan University of Medical Sciences (Alzahra and Shahid Beheshti Hospital) Timing: December 2012 to November 2013
Interventions	Breast milk supplemented with 9:1 mixture of short‐chain galacto‐oligosaccharide/long‐chain fructo‐oligosaccharide (n = 25) vs unsupplemented breast milk (n = 50) Not clear when the intervention ceased
Outcomes	Primary outcomes: incidence of suspected NEC Secondary outcomes: milk volumes, feeding intolerance (presence of milk in the stomach 2 hours after a meal, i.e. gastric residue), abdominal distension, postnatal age when full enteral feeding was attained, death, length of hospital stay, weight at day 30, associated patent ductus arteriosus, and intraventricular haemorrhage
Notes	Conflicts of interest: none declared, but Nutricia MMP, Mashad, Iran is acknowledged. Source of support: This paper is derived from a residency thesis (No. 392237) at Isfahan University of Medical Sciences. No details of source of funding are provided. Study authors published 2 reports of the same trial but reported different methods regarding blinding and randomisation, and included different numbers of infants. The first publication reported quasi‐randomisation and lack of blinding of caregivers, and the second publication reported computer‐generated randomisation and blinding of the investigator and nurse. Study authors confirmed via email that publications described the same trial, but they have not yet clarified the different methods reported. We chose to include details from the first publication, as it involved a larger sample size and assessed outcomes relevant to this review.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Infants were randomised based on files ending in odd or even numbers. It is not clear how the 2:1 allocation was achieved.
Allocation concealment (selection bias)	High risk	Randomisation was done by an independent employee, but allocation was not blinded and could be predicted.
Blinding of participants and personnel (performance bias) All outcomes	High risk	Study authors stated, "care providers were not blinded to an infant's protocol".
Blinding of outcome assessment (detection bias) All outcomes	Unclear risk	Suspected NEC diagnosis was clinical and therefore was potentially subject to bias. However, it is unclear whether outcome assessors were among the care providers who were not blinded.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Losses to follow‐up were disclosed as follows: of 131 eligible infants, 24 were excluded for having major congenital anomalies, gastrointestinal system anomalies, asphyxia, or sepsis, and parents of 19 infants refused to participate or were transferred to other wards. Of 88 infants randomised, 13 (9 in the prebiotic group and 4 in the control group) were transferred to other departments. The 13 excluded after randomisation appear to be attributable to reasonable attrition. However, the reasons for transfer, which could be related to outcomes assessed, were not stated. It also was not clear whether study authors compared baseline characteristics between participants included and excluded from the study. One loss to follow‐up and 1 death occurred in each group, but these appear to be included in the analysis, although the 13 transferred to other departments were excluded, making it difficult to determine whether an intention‐to‐treat approach was used.
Selective reporting (reporting bias)	Low risk	The study protocol was not available, but researchers reported results for all outcomes listed in the methods.
Other bias	High risk	Study authors published 2 reports of the same trial that described different methods and different numbers of included infants. We were unable to reproduce their analyses from the published data.

NEC: necrotising enterocolitis.

NICU: neonatal intensive care unit.