Do probiotics lower the risk of death in premature babies?
Yes, for babies born at 28 to 31 weeks. In a Swedish study of 4,695 very premature babies, those given a daily probiotic had about 84% lower risk of death and about 75% lower risk of a dangerous gut disease. The study shows a strong link, but it was not a randomized trial.
The gut disease is called necrotizing enterocolitis, or NEC. In NEC, part of a premature baby’s bowel becomes inflamed and can start to die. Probiotics are live “friendly” bacteria, and the hope is that they help protect a preemie’s immature gut.
In 2020, the Swedish Neonatal Society recommended that every baby born very preterm (28 weeks 0 days to 31 weeks 6 days) get probiotics. Before that recommendation, no baby in the study received them. By 2021 to 2024, about 65% did. That shift gave researchers a natural comparison across the whole country.
What the data show
The probiotic was a daily dose of three strains, Bifidobacterium infantis, Bifidobacterium lactis, and Streptococcus thermophilus. Babies started it after birth and stopped at 34 weeks of development.
Death occurred in 0.3% of babies who got the probiotic, compared with 1.4% of those who did not. After adjusting for differences between the groups, that is about 84% lower risk (adjusted relative risk 0.16). The true reduction was very likely somewhere between 55% and 94% (95% CI 0.06 to 0.45). In raw numbers, that gap works out to about 11 fewer deaths for every 1,000 babies.
NEC followed the same pattern. It struck 0.6% of the probiotic group and 2.5% of the others, about 75% lower risk (adjusted relative risk 0.25). The true reduction was very likely between 39% and 90% (95% CI 0.10 to 0.61). That is roughly 19 fewer cases per 1,000 babies, or about 1 case prevented for every 53 babies treated.
Blood infections told a different story. The combined rate of death or culture-proven sepsis was 3.4% with probiotics and 4.4% without (adjusted relative risk 0.86). That range ran from 42% lower to 26% higher risk, so the study could not show a clear effect on infections.
Dr. Kumar’s Take
This study measured the outcomes that matter most: whether babies lived and whether they developed NEC. The numbers come from Sweden’s national neonatal register, which covers everyday care across the country rather than one hospital.
The researchers also asked how the probiotic might save lives. Their modeling suggested about 42% of the drop in deaths ran through fewer cases of NEC. That estimate was very uncertain, anywhere from about 16% to all of it. Still, it fits the biology. Fewer babies with a dying bowel should mean fewer babies dying.
I find the sepsis result reassuring rather than disappointing. Giving live bacteria to fragile newborns raises an obvious question about infection. Here, the rate of death or sepsis did not go up.
How strong is the evidence?
This was an observational study. Babies were not randomly assigned to get probiotics. Other things may also have changed between 2017 and 2024, and those changes could explain part of the benefit. The researchers tested their results several ways, including matching similar babies and weighting the groups, to see if the finding held.
The results apply only to babies born at 28 to 31 weeks. The authors state plainly that they should not be extended to extremely preterm babies born before 28 weeks. Those tiny infants need their own evidence. The study also excluded babies who died in their first 3 days of life.
Practical Takeaways
- If your baby is born at 28 to 31 weeks, ask the neonatal team whether they use a probiotic and which strains they give.
- Probiotics for preemies are specific products given in the hospital under medical supervision, so do not substitute an over-the-counter supplement on your own.
- If your baby was born before 28 weeks, this study does not answer the question, and the decision needs a separate talk with the care team.
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FAQs
What is necrotizing enterocolitis in premature babies?
Necrotizing enterocolitis, or NEC, is a disease where part of the intestine becomes inflamed and the tissue can die. It mostly affects premature babies. The most severe cases need surgery. In this study, NEC was counted when it reached a moderate or severe stage, and the most severe, surgical stage was tracked separately.
Which probiotic was used for preterm babies in Sweden?
The Swedish babies received a daily probiotic containing three strains: Bifidobacterium infantis, Bifidobacterium lactis, and Streptococcus thermophilus. The dose was 1 billion colony-forming units, a standard measure of how many live bacteria are in a dose. It was started after birth and stopped at 34 weeks of development. Different probiotic products contain different strains, so these results belong to this specific mix.
Are probiotics safe for premature babies?
In this study, babies who got probiotics did not have a higher rate of death or blood infection confirmed by a lab culture. The rate was 3.4% with probiotics and 4.4% without, and that difference was too small to call real. That is a useful safety signal for a treatment made of live bacteria. It applies to babies born at 28 to 31 weeks, not to the smallest and sickest preemies.
Bottom Line
Across all of Sweden, very premature babies given a daily three-strain probiotic had about 84% lower risk of death and about 75% lower risk of necrotizing enterocolitis, with no rise in serious infections. Because the study was observational, it cannot prove the probiotic caused the benefit. It is still strong real-world evidence that probiotics help babies born at 28 to 31 weeks.
