Too many antibiotics can give preemies a lifetime of ill health Today, babies born as early as

Too many antibiotics can give preemies a lifetime of ill health 

Today, babies born as early as 28 weeks routinely survive, as do more than half of those born at 24 weeks (although often with significant disabilities). Much of the credit goes to antibiotics, which have thwarted infections such as sepsis and group B strep that a preemie’s immature immune system could not have fought on its own. Those successes spurred a steady increase in routine antibiotic use in the NICU. At last count, three of the top four drugs prescribed in the NICU were antibiotics.

Over time, however, scientists began noticing that antibiotics can increase babies’ risk of the very afflictions the drugs aim to protect against—such as fungal infections, late-onset sepsis, and a deadly intestinal disorder called necrotizing enterocolitis. In a seminal 2009 study in Pediatrics, for example, Greenberg’s colleague Michael Cotten showed that each additional day of antibiotics significantly increased the odds that a preemie would develop necrotizing enterocolitis or die.

Researchers are still debating when the first microbes colonize us—in utero or during birth—but Greenberg and many others worry that early use of antibiotics in infants disrupts the establishment of those indispensable residents. The gut microbiome is practically an organ unto itself, weighing about as much as the liver. It is thought to play a critical role in priming the immune system, and it produces just as many neurotransmitters as the human brain. Genetic and environmental factors, including antibiotics, shape its makeup early in life. Then, around age 3, a quasi-stability sets in and we are “stuck with that architecture,” says Gautam Dantas, a microbiologist at Washington University in St. Louis, Missouri.