Babies born too early (especially before 34 weeks) need a great deal of special care and are vulnerable to many health problems, including infection. They may need help with breathing and feeding, if their organs are not sufficiently developed to do these jobs independently.

One serious problem for preemies is an infection affecting the digestive system, called necrotizing enterocolitis. This affects about 7 in 100 babies born prematurely. One theory is that premature babies are vulnerable to this because they don’t have sufficient healthy bacteria in their intestines, to prevent colonization by other, more dangerous bacteria.

So doctors have been looking at giving preemies a supplement containing healthy bacteria. These types of supplements are often called probiotics. You may have seen them advertised as yogurts, or fermented milk drinks.

A new summary of the research on these trials seems to show that they work well. They seem to reduce the risk of premature babies getting necrotizing enterocolitis by about 35 percent. Indeed, the researchers say it’s time all preemies were given probiotics routinely, to reduce the risk.