Guney‐Varal 2017.

Study characteristics
Methods	RCT
Participants	110 preterm (< 33 weeks) or VLBW infants
Interventions	Synbiotics (N = 76): Lactobacillus rhamnosus (4 × 10⁸ cfu) + L. casei (8 × 10⁸ cfu) + L. plantorum (4 x10⁸ cfu) + Bifidobacterium animalis (4 × 10⁸ cfu) plus FOS (383 mg) and GOS (100 mg) added to human milk or formula daily until hospital discharge Control (N = 43): no synbiotic supplement
Outcomes	NEC Death Invasive infection Length of hospital stay
Notes	Turkey (single centre: 2013 to 2016) Funding: not stated
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	High risk	Quote. “Alternate randomization” (quasi‐randomised)
Allocation concealment (selection bias)	High risk	Quote: “Alternate randomization”
Blinding of participants and personnel (performance bias) All outcomes	High risk	Unmasked
Blinding of outcome assessment (detection bias) All outcomes	High risk	Unmasked
Incomplete outcome data (attrition bias) All outcomes	Low risk	Complete reporting for primary outcomes
Selective reporting (reporting bias)	Low risk	No access to protocol but unlikely
Other bias	High risk	Differences in baseline birth weight (1728 versus 1228 g), but no difference in gestational age at birth (29.7 versus 29.3 weeks)