Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Coding to group 1 and 2 was done by a faculty of another department not related to this study. First case was selected to 1 group by lottery method and subsequent group was continued accordingly
Allocation concealment (selection bias)	Low risk	Participants and investigators did not know group allocation
Blinding of participants and personnel (performance bias)	Low risk	Probiotics were added to breast milk by registrar or assistant registrar of the corresponding unit before feeding
Blinding of outcome assessment (detection bias)	Low risk	Participants and investigators did not know group allocation
Incomplete outcome data (attrition bias)	Low risk	15% attrition. Reasons for loss to follow up reported.
Selective reporting (reporting bias)	Low risk	All expected outcomes were reported
Other bias	Low risk	No concerns for other risk of bias