Table 6.

Year at which the last participant of the study was enrolled.

Intervention	Outcome	Year last participant enrolled
Bifidobacterium animalis subsp. lactis	NEC, duration of hospitalization	2014, 2010, 2005, 2003
Lactobacillus reuteri	Duration of hospitalization	2013, 2013, 2012, 2011, 2007
Lactobacillus spp., Bifidobacterium spp., and Saccharomyces boulardii	Days to reach full feed	2016, 2013
Lactobacillus spp. and Bifidobacterium spp.	NEC, all-cause mortality	2013, 2013, 2012, 2009, 2008, 2008, 2007, 2007, 2003
All studies		Median: 201.5 (11.5 years ago), IQR: 9–15 years; Mean: 2009.85 (12.15 years ago), SDL 3.73 years

**If the outcome cited in Morgan et al.³¹ was categorized as primary or secondary in the original paper, we noted it as such. If the outcome was not specifically designated as secondary in a paper in which another outcome was primary, we described it as outcome category unclear, but not primary.

^‡https://clinicaltrials.gov/. There should not be a “.” after this url as it causes problems when pasting it into a browser.

^¶ctri.nic.in. There should not be a “.” after this url as it causes problems when pasting it into a browser.

^§isrctn.com. There should not be a “.” after this url as it causes problems when pasting it into a browser.