Can probiotics prevent necrotizing enterocolitis in preterm babies?

How much can probiotics reduce the risk of NEC and death?

The short answer is: by a lot. The most comprehensive analysis available — a 2023 Cochrane review of 60 randomized trials involving over 11,000 very preterm or very low birth weight infants — found that probiotics reduced the risk of NEC by about 46% (risk ratio 0.54). In practical terms, this means that for every 33 babies treated with probiotics, one case of NEC would be prevented. The same review showed a 23% reduction in all-cause mortality (risk ratio 0.77), meaning one death would be prevented for every 50 babies treated. These findings are echoed by a 2025 umbrella meta-analysis of 35 meta-analyses, which reported a 49% reduction in NEC and a 28% reduction in mortality. The consistency across these large, high-quality reviews makes the evidence compelling.

The benefit appears even more pronounced in some individual trials. For example, a 2022 randomized controlled trial of a multi-strain probiotic found that none of the 50 babies in the probiotic group developed NEC, compared to 5 of 50 in the placebo group. Another 2022 trial reported NEC in only 2.1% of the probiotic group versus 11.9% of controls. While these are smaller studies, they align with the overall trend seen in the meta-analyses.

Do all preterm babies benefit equally?

The evidence is strongest for very preterm (born before 32 weeks) or very low birth weight (under 1500 grams) infants. The 2023 Cochrane review found clear benefits in this group. However, for extremely preterm or extremely low birth weight babies (born before 28 weeks or under 1000 grams), the picture is less certain. In that subgroup, the same review found that probiotics may have little or no effect on NEC (risk ratio 0.92) or mortality (risk ratio 0.92), though the number of babies studied was much smaller (about 1,800), so the evidence is less reliable. This means that while probiotics are a proven strategy for the broader preterm population, their effectiveness in the tiniest, most fragile infants is still an open question.

The type of feeding also matters. A 2021 network meta-analysis found that the probiotic strain Bifidobacterium lactis Bb-12/B94 was particularly effective at reducing NEC in babies fed exclusively human milk (odds ratio 0.04) compared to those receiving formula (odds ratio 0.32). This suggests that probiotics work best alongside breast milk, which itself provides protective factors.

Which probiotic strains or combinations are most effective?

Multi-strain probiotics appear to outperform single-strain preparations. The 2025 umbrella meta-analysis specifically noted that multi-strain combinations were more effective than single strains for preventing NEC and reducing mortality. A 2019 meta-analysis of 34 studies (over 9,000 infants) found that probiotic mixtures reduced NEC incidence to 2.48% compared to 3.54% for single strains, and also lowered sepsis rates more effectively. Common effective combinations include Bifidobacterium plus Lactobacillus, sometimes with Streptococcus. The 2021 network meta-analysis highlighted Lactobacillus acidophilus LB as the single most promising strain for reducing NEC risk (odds ratio 0.03), but this was based on limited data.

It is important to note that not all probiotics are created equal. The 2023 Cochrane review found that the specific formulations varied widely across trials, and the quality of evidence for individual strains is often low. This means that while the overall class of probiotics works, we don't yet know the single best recipe. Hospitals that adopt probiotics should choose a product with published evidence from randomized trials.

Are probiotics safe for preterm babies?

Yes, the evidence consistently shows that probiotics are safe for preterm infants. Across all the major reviews, probiotics did not increase the risk of late-onset invasive infections (sepsis). The 2023 Cochrane review found a small but statistically significant reduction in sepsis (risk ratio 0.89), and the 2015 Cochrane review reported no cases of systemic infection caused by the probiotic organisms themselves. A 2015 meta-analysis of 27 trials also found no increase in sepsis risk (risk ratio 0.94). This safety profile is reassuring, especially given the devastating consequences of NEC.

However, caution is warranted for extremely preterm infants, where the data on both efficacy and safety are thinner. The 2023 Cochrane review noted that in this subgroup, the effect on infection was uncertain (risk ratio 0.93). Additionally, the quality of manufacturing and storage of probiotics matters — contamination or improper dosing could pose risks. For this reason, any use of probiotics in neonatal intensive care should follow strict protocols and use products from reputable manufacturers.

About These Sources

This answer is built on 11 peer-reviewed studies — published from 2015 to 2025, 2 from 2024 or later, 5 in Q1 journals, collectively cited 245 times — selected as the most relevant from 11 studies that passed quality screening, drawn from 36 papers retrieved from a database of over 500 million.

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