| Study | Reason for exclusion |
|---|---|
| Arora 2017 | Most participants not very preterm or VLBW. |
| Awad 2010 | Most participants not very preterm or VLBW. |
| Chi 2019 | Not an RCT. |
| Dasopoulou 2015 | RCT of prebiotics. |
| Deng 2010 | Most participants not very preterm or VLBW. |
| Denkel 2016 | Not an RCT. |
| Di 2010 | Most participants not very preterm or VLBW. |
| Dongol‐Singh 2017 | Most participants not very preterm or VLBW. |
| Hua 2014 | Most participants not very preterm or VLBW. |
| Hussain 2016 | Most participants not very preterm or VLBW. |
| Kaban 2019 | Most participants not very preterm or VLBW. |
| Ke 2008 | Most participants not very preterm or VLBW. |
| Koksal 2015 | RCT of synbiotics |
| Moles 2015 | A pilot study with including 5 infants. |
| Partty 2013 | Most participants not very preterm or VLBW. |
| Qiao 2017 | Most participants not very preterm or VLBW. |
| Rojas 2012 | Most participants not very preterm or VLBW. |
| Romeo 2011 | Most participants not very preterm or VLBW. |
| Shujie 2011 | Most participants not very preterm or VLBW. |
| Sinha 2015 | Most participants not very preterm or VLBW. |
| Thanhaeuser 2014 | Not an RCT. |
| Uhlemann 1999 | Most participants not very preterm or VLBW. |
| Underwood 2014 | RCT of prebiotics |
| Xu 2016 | Most participants not very preterm or VLBW. |
| Zhou 2012 | Most participants not very preterm or VLBW. |
| Zhuang 2007 | Most participants not very preterm or VLBW. |
RCT: randomised controlled trial; VLBW: very low birth weight