Mom's breast milk can be altered by antibiotics in ways that might harm an infant's health, according to a new study.
The Canadian researchers were particularly concerned with an increase in bacteria that can be harmful, namely a bacterium called Pseudomonas that can cause a serious intestinal infection called necrotizing enterocolitis in a preterm infant.
About 7% of preterm infants develop this frequently fatal condition, in which part of the bowel dies. Also, a class of antibiotics called cephalosporins had a significant dampening effect on the diversity of microbiota in breast milk, the researchers noted.
"The bacteria in breast milk has the potential to transfer to a preterm infant's gut and shape their short- and long-term health and development," explained lead researcher Michelle Asbury, from the department of nutritional sciences at the University of Toronto.
"Although we observed changes in the breast milk bacteria based on maternal factors, research is now needed to see whether these changes impact infant health," she added.
For the study, Asbury and her colleagues looked at 490 samples of breast milk from 86 mothers of preterm infants.
The mother's weight and type of delivery had an influence on the microbiota in the breast milk. But antibiotics, particularly when taken for weeks, had effects on microbes that play a role in disease, gut health and processes that aid in growth and development, the researchers found.
"The understanding of maternal breast milk of mothers who deliver a preterm infant is a vastly understudied area," said Dr. Mitchell Kramer, chairman of the department of obstetrics and gynecology at Northwell Health Huntington Hospital in Huntington, N.Y.
"This study sheds some light on the understanding and importance of this issue," said Kramer, who wasn't involved with the research. "Additional studies are now needed to understand whether these observed changes in the microbial content of breast milk translate into changes in infant GI colonization and long-term health outcomes of preterm infants, especially with the high rate of morbidity and developmental challenges in this vulnerable population."
Still, Asbury stressed, "Despite the changes we observed in the breast milk bacteria from antibiotics, mothers should continue taking antibiotics that are prescribed by their physician while also providing breast milk to their infant when possible.
"However, we hope our findings will encourage discussions among physicians to carefully choose which antibiotics they prescribe and for how long," she said.
Asbury's report was published online Sept. 3 in the journal Cell Host & Microbe.
Dr. Jennifer Wu, an obstetrician-gynecologist at Lenox Hill Hospital in New York City, looked over the study findings and said that breast milk is important for promoting gut flora in babies.
"For premature infants who may have serious intestinal issues like necrotizing enterocolitis, this is especially true," she said.
This study highlights different changes that can occur in the makeup of the breast milk, Wu said.
"Some of the factors such as mode of delivery may not be alterable. Others such as maternal weight could be affected by encouraging patients to achieve ideal body weight for pregnancy. Caution in giving mothers antibiotics would be a good practice for both mother and baby," she said.
For more on breast milk, see the American Pregnancy Association.